The Apple Watch and Resting Calories

Update: Since I wrote this article, Apple has changed the way the Apple Watch and the Health app calculate BMR. It is no longer the ridiculously high amount I mention below; for me, it is around 2,200 calories each day, but it still varies.

I’ve highlighted how the Apple Watch isn’t very accurate as a fitness tracker, and I’ve shown that my Apple Watch’s heart rate sensor doesn’t work correctly, which is leading Apple to exchange it.

But one thing I find surprising is the way the Apple Watch – or, more correctly, the Activity app on your iPhone – calculates resting calories. This is another term for basal metabolic rate, or BMR, the amount of energy your body expends just to keep you alive. If you did absolutely nothing during a day, other than sleep, your body would still burn a certain number of calories. In fact, your active calories only represent a small part of the amount of energy you use.

Like many such measurements that are difficult to measure, the BMR varies according to the way it’s calculated. But one such calculator tell me that may BMR is 2008 calories. Another one, at myFitnessPal, tells me my BRM is 1894 calories.

Resting caloriesNot Apple. According to the Activity app, my resting calories for the full day yesterday was 3184, or 50% more than a BMR calculator. As such, the Activity app tells me that I burned 3829 calories yesterday, with 645 of these being active calories. Yesterday, I took two brisk walks: one on my treadmill, for 30 minutes, which counted as 178 calories, and one outdoors, for about 20 minutes, which clocked 83 calories.

It’s interesting that the 20-minute outdoor walk only counted for about half as much as the 30-minute indoor walk, which measured calories based on my heart rate, and, presumably, the frequency of my steps.

No matter how you slice it, these numbers are wrong. I’ll give Apple a pass on the active calories; there’s no way to get those numbers down precisely. But the BMR, or resting calories? I’ve entered my data in the health app – age, height, weight and sex – so, unless online calculators are way off the mark, Apple has some tweaking to do.

What’s also surprising is that this number isn’t the same every day; it ranges from 3172 to 3195. This is a fixed number, that has nothing to do with my activity. There’s not a big difference between the top and bottom of the scale, but they should be the same every day. Only the active calories should change. (Update: this is because my weight changes slightly every day; I use a wireless scale which syncs its data to HealthKit.)

And this is particularly worrisome. This number is based on a very simple calculation, and isn’t skewed by the way you move your arms, or your stride when you walk. It’s the one number that they should get right.

60 thoughts on “The Apple Watch and Resting Calories

    • But it’s not the watch that calculates resting calories, it’s the Activity app. So it can’t be a problem with the watch itself. Many other users see this problem too.

    • But it’s not the watch that calculates resting calories, it’s the Activity app. So it can’t be a problem with the watch itself. Many other users see this problem too.

  1. Seems to me that the resting calories should vary each day since you would subtract the amount of time active calories are counted. If there is a calculated max of 2,400 per 24 hours (100/hr) and you were active for 1 hour, I would expect the resting calories to be 2,300 that day, not 2,400…

    • No, active calories are counted in addition to resting calories when you’re active. You can see this in the Activity app on the iPhone if you’ve recorded any workouts; the app shows the amount of active calories, and resting calories, for the period of the workout.

      • I know this is an old thread, but I am exploring how the Apple Watch works relative to health. I don’t think that resting calories has the same definition as BMR. Resting calories represent anything you are doing that is not exercise. The app literally records your heart rate every single minute… One minute, sitting motionless in a chair, you will burn .2 calories. If you lean forward in your chair the next minute, and your heart rate goes up a tad, you might burn .7 calories. The Health App adds up all of these minute-by-minute caloric expenditures during the day to arrive at both your active and resting calories.

        • No, that’s incorrect. It only checks your heartbeat every 10 minutes, and only if you’re not moving at the time. The exception is if you are doing a workout, during which it checks your heart rate continuously.

          • Kirk, go into your Health app, not the Activity app. Health Data > Fitness > Resting Energy > Show All Data. You can see the data points being added. Click into them. The total of those daily data points should match your Activity app. total. In my case, there’s a new data point from my watch almost every minute of the day. When I’m not wearing the watch, the data points entered appear to be an average. This would explain the daily variance. I believe you’re assuming a static daily formula based on fixed measurements rather than considering fluctuating input from the Watch sensor by minute. Btw, my high and low fluctuates in line with yours and my Apple Resting Energy is lower than in the BMR apps you linked to. Also has nothing to do with your wifi scale, I don’t use one, or manually updating your weight daily. I don’t do that either. Also, I don’t see where Apple has ever claimed this to be a standard BMR calculation.

            • If you look at the data, you’ll see it looks like random numbers, and you can see that it’s not added every second. The precise time it’s added isn’t specified, so sometimes you don’t have an entry for a given second. When you look at the total by day, it’s stable; the only variant would be your weight.

  2. Seems to me that the resting calories should vary each day since you would subtract the amount of time active calories are counted. If there is a calculated max of 2,400 per 24 hours (100/hr) and you were active for 1 hour, I would expect the resting calories to be 2,300 that day, not 2,400…

    • No, active calories are counted in addition to resting calories when you’re active. You can see this in the Activity app on the iPhone if you’ve recorded any workouts; the app shows the amount of active calories, and resting calories, for the period of the workout.

      • I know this is an old thread, but I am exploring how the Apple Watch works relative to health. I don’t think that resting calories has the same definition as BMR. Resting calories represent anything you are doing that is not exercise. The app literally records your heart rate every single minute… One minute, sitting motionless in a chair, you will burn .2 calories. If you lean forward in your chair the next minute, and your heart rate goes up a tad, you might burn .7 calories. The Health App adds up all of these minute-by-minute caloric expenditures during the day to arrive at both your active and resting calories.

        • No, that’s incorrect. It only checks your heartbeat every 10 minutes, and only if you’re not moving at the time. The exception is if you are doing a workout, during which it checks your heart rate continuously.

          • Kirk, go into your Health app, not the Activity app. Health Data > Fitness > Resting Energy > Show All Data. You can see the data points being added. Click into them. The total of those daily data points should match your Activity app. total. In my case, there’s a new data point from my watch almost every minute of the day. When I’m not wearing the watch, the data points entered appear to be an average. This would explain the daily variance. I believe you’re assuming a static daily formula based on fixed measurements rather than considering fluctuating input from the Watch sensor by minute. Btw, my high and low fluctuates in line with yours and my Apple Resting Energy is lower than in the BMR apps you linked to. Also has nothing to do with your wifi scale, I don’t use one, or manually updating your weight daily. I don’t do that either. Also, I don’t see where Apple has ever claimed this to be a standard BMR calculation.

            • If you look at the data, you’ll see it looks like random numbers, and you can see that it’s not added every second. The precise time it’s added isn’t specified, so sometimes you don’t have an entry for a given second. When you look at the total by day, it’s stable; the only variant would be your weight.

  3. I have the same problem, yesterday my resting calories were 1808 and today it was 1705.

    But I just realized that the time you physically take off the watch can vary the resting calories as well. For example, if I took my watch off at midnight and it was 1808, yet the next day I took my watch off at 10pm, then my BMR would be lower because I did not have it on for the remaining two hours of the day. Theoretically, they should just keep it the same every day and show the same BMR at the end of the day regardless of what time the watch was physically removed, however, they may not do this.

    • If I look in the Activity app at days where I only wore the watch for a few hours, my resting calories are roughly the same. They shouldn’t change from day to day; the number is for the full day, not the time you wear the watch.

  4. I have the same problem, yesterday my resting calories were 1808 and today it was 1705.

    But I just realized that the time you physically take off the watch can vary the resting calories as well. For example, if I took my watch off at midnight and it was 1808, yet the next day I took my watch off at 10pm, then my BMR would be lower because I did not have it on for the remaining two hours of the day. Theoretically, they should just keep it the same every day and show the same BMR at the end of the day regardless of what time the watch was physically removed, however, they may not do this.

    • If I look in the Activity app at days where I only wore the watch for a few hours, my resting calories are roughly the same. They shouldn’t change from day to day; the number is for the full day, not the time you wear the watch.

    • Exactly, the only variant in calculating the BMR formula is your day-to-day weight. My resting calories change everyday because I update my weight everyday in the Health app.

      My big wish is for Apple to add body fat percentage into the resting calorie formula because that can alter it significantly. I use one of the handheld devices to measure my body fat %. A person’s metabolism ultimately determines most of your resting calories, and that’s all genetics, so that just goes to show this is all just a guessing game anyways.

    • Exactly, the only variant in calculating the BMR formula is your day-to-day weight. My resting calories change everyday because I update my weight everyday in the Health app.

      My big wish is for Apple to add body fat percentage into the resting calorie formula because that can alter it significantly. I use one of the handheld devices to measure my body fat %. A person’s metabolism ultimately determines most of your resting calories, and that’s all genetics, so that just goes to show this is all just a guessing game anyways.

  5. You’re not correct to say that resting calories are always the same. For instance, if you do 20 mins of high intensity interval training, you’ll see a spike in Resting Energy Expenditure (REE) for up to 24 hours.

  6. You’re not correct to say that resting calories are always the same. For instance, if you do 20 mins of high intensity interval training, you’ll see a spike in Resting Energy Expenditure (REE) for up to 24 hours.

  7. This is a known bug with the activity app.

    I’ve had it confirmed to me by Apple support.

    My suspicion is they’re using lb/in in a formula that expects kg/cm

  8. This is a known bug with the activity app.

    I’ve had it confirmed to me by Apple support.

    My suspicion is they’re using lb/in in a formula that expects kg/cm

  9. Any news on this topic?
    I’ve bought my apple watch this week and I’m unhappy to see how it overestimate my resting calories and it underestimate my active calories 🙁

  10. Any news on this topic?
    I’ve bought my apple watch this week and I’m unhappy to see how it overestimate my resting calories and it underestimate my active calories 🙁

  11. Resting calories are a generality in apps. Resting calories vary with composition. Fat burns burns less calories than lean tissue, lean tissue more than fat tissue.
    Resting calories of people with identical weight would be greater for the person with less body fat.

  12. Resting calories are a generality in apps. Resting calories vary with composition. Fat burns burns less calories than lean tissue, lean tissue more than fat tissue.
    Resting calories of people with identical weight would be greater for the person with less body fat.

  13. Does anyone know how to remove the calorie counter from the watch? I use the other trackers – but don’t need/don’t want the calorie counter. I don’t want to lower or raise the number of calories (I know how to manipulate the goals). I’d like to delete the calories and save some battery. I’ve burned a lot of calories trying to figure this out on my own. Appreciate your help.

  14. Does anyone know how to remove the calorie counter from the watch? I use the other trackers – but don’t need/don’t want the calorie counter. I don’t want to lower or raise the number of calories (I know how to manipulate the goals). I’d like to delete the calories and save some battery. I’ve burned a lot of calories trying to figure this out on my own. Appreciate your help.

  15. Is it possible that the “resting calories” counts all the time when you’re not literally tracking a workout? So for instance, one day I’m walking around a lot at work (in a hospital) and I lift a bunch of things and go up and down a few flights of stairs. Then I go home and do my normal 25 minute workout. Another day I don’t move as much at work or I’m in the car for a longer stretch than usual. Then I go home and do the same workout.

    The app automatically counts some moving time as exercise but we don’t know that formula either, so perhaps the “resting” calories isn’t exactly BMR but more based on the “non-workout” activity we did on a given day?

    I’m still trying to figure this out after a year. I have a calorie goal of 900 (that I only hit when I am active at work all day AND exercise) and I don’t track my calories, but if I did, I’m not exactly sure how the ~900 really counts towards my daily intake and output.

    Idk, maybe I’m dumb.

    Let me know what you think.

    • No, as I explain, resting calories are what your body burns to keep you alive. It’s everything other than movement. And, anyway, counting calories is a bit useless, since a) calorie counts for foods are just estimates, and b) we don’t necessarily get all the calories in certain foods. It’s a rough estimate at best, but one that scientists increasingly realize is way off the mark.

      • I disagree. Counting calories isn’t useless. Yes, it is near impossible to be completely accurate, but having a general idea of the calories you are putting in your body vs. the calories out can be very beneficial. I’ve been counting calories off and on for over a decade. It is the only way I have been able to lose weight and keep it off.

  16. Is it possible that the “resting calories” counts all the time when you’re not literally tracking a workout? So for instance, one day I’m walking around a lot at work (in a hospital) and I lift a bunch of things and go up and down a few flights of stairs. Then I go home and do my normal 25 minute workout. Another day I don’t move as much at work or I’m in the car for a longer stretch than usual. Then I go home and do the same workout.

    The app automatically counts some moving time as exercise but we don’t know that formula either, so perhaps the “resting” calories isn’t exactly BMR but more based on the “non-workout” activity we did on a given day?

    I’m still trying to figure this out after a year. I have a calorie goal of 900 (that I only hit when I am active at work all day AND exercise) and I don’t track my calories, but if I did, I’m not exactly sure how the ~900 really counts towards my daily intake and output.

    Idk, maybe I’m dumb.

    Let me know what you think.

    • No, as I explain, resting calories are what your body burns to keep you alive. It’s everything other than movement. And, anyway, counting calories is a bit useless, since a) calorie counts for foods are just estimates, and b) we don’t necessarily get all the calories in certain foods. It’s a rough estimate at best, but one that scientists increasingly realize is way off the mark.

      • I disagree. Counting calories isn’t useless. Yes, it is near impossible to be completely accurate, but having a general idea of the calories you are putting in your body vs. the calories out can be very beneficial. I’ve been counting calories off and on for over a decade. It is the only way I have been able to lose weight and keep it off.

  17. I have been using an Apple Watch 2 (currently, watchOS 3.2.3) for the past 9 months, wearing it to bed and charging it for usually not more than an hour a day, after breakfast or before bed. According to the Health app on my iPhone 7+ (iOS 10.3.3), the daily average for “resting energy” across these 9 months is 1520 kcal. The range over the month of July was 1484-1675 kcal. The Health app reports values for resting energy every 5 minutes. I have not confirmed this across multiple samples, but it appears to interpolate estimates for these values when the watch is being charged, since I did not see a gap in data during a known period of charging, i.e., with the watch off my wrist and thus not recording HR or movement. I find that my hourly resting energy is always the lowest during the hours between midnight and 6 am., when I am sleeping and my HR rate measured by the watch is always the lowest. The peak values for the day vary by amplitude and time, ranging up to 40% higher and often occurring near midday. But they do not correspond in any obvious way to when I am overtly active, other than being awake. The lowest values when I am in bed are ~58 kcal/hr, which corresponds to a projected minimum daily value of 1392 kcal/day, if I slept all day. Interestingly, this is slightly below the BMR values I get from the online sources Kirk suggests: 1421 from the bmi-calculator and 1436 from MyFitnessPal, based strictly on my height, weight, age, and gender. In turn, these BMR estimates are lower than what I see on average in the Health app, although only by about 6%. So, in my experience, I think it is clear that Apple’s concept of “resting energy” does not correspond strictly to standard BMR, but reflects something more dynamic about my body’s non-active resting state. It is not merely the state of being alive, but much more, involving changes in HR and body position, including some episodic movement that can reasonably be distinguished from the active energy that is part of more sustained movement, including, but not restricted to, active exercise. As a biologist, this makes a great deal of sense to me.

    • Something else to consider is that BMR calculations are just that, calculations, and don’t take into account the impact of lean mass vs fat mass, or body composition. (someone mentioned this earlier).

      “unless online calculators are way off the mark,”

      Anytime I perform a metabolic resting assessment on someone and the resulting measurement is close to a calculated BMR result, I play the lottery, because apparently coincidences are lining up for me that day!

  18. I have been using an Apple Watch 2 (currently, watchOS 3.2.3) for the past 9 months, wearing it to bed and charging it for usually not more than an hour a day, after breakfast or before bed. According to the Health app on my iPhone 7+ (iOS 10.3.3), the daily average for “resting energy” across these 9 months is 1520 kcal. The range over the month of July was 1484-1675 kcal. The Health app reports values for resting energy every 5 minutes. I have not confirmed this across multiple samples, but it appears to interpolate estimates for these values when the watch is being charged, since I did not see a gap in data during a known period of charging, i.e., with the watch off my wrist and thus not recording HR or movement. I find that my hourly resting energy is always the lowest during the hours between midnight and 6 am., when I am sleeping and my HR rate measured by the watch is always the lowest. The peak values for the day vary by amplitude and time, ranging up to 40% higher and often occurring near midday. But they do not correspond in any obvious way to when I am overtly active, other than being awake. The lowest values when I am in bed are ~58 kcal/hr, which corresponds to a projected minimum daily value of 1392 kcal/day, if I slept all day. Interestingly, this is slightly below the BMR values I get from the online sources Kirk suggests: 1421 from the bmi-calculator and 1436 from MyFitnessPal, based strictly on my height, weight, age, and gender. In turn, these BMR estimates are lower than what I see on average in the Health app, although only by about 6%. So, in my experience, I think it is clear that Apple’s concept of “resting energy” does not correspond strictly to standard BMR, but reflects something more dynamic about my body’s non-active resting state. It is not merely the state of being alive, but much more, involving changes in HR and body position, including some episodic movement that can reasonably be distinguished from the active energy that is part of more sustained movement, including, but not restricted to, active exercise. As a biologist, this makes a great deal of sense to me.

    • Something else to consider is that BMR calculations are just that, calculations, and don’t take into account the impact of lean mass vs fat mass, or body composition. (someone mentioned this earlier).

      “unless online calculators are way off the mark,”

      Anytime I perform a metabolic resting assessment on someone and the resulting measurement is close to a calculated BMR result, I play the lottery, because apparently coincidences are lining up for me that day!

  19. Its pretty useless to assume that the term resting calories means the same thing as basal metabolic rate. Apple watch appears to captures both the basal (as shown by their sleep values which are crudely identical across the night, and then during the day it is also capturing some of the activity (which could be thought of as a combination of the Non-exercise activity thermogenesis (neat) plus likely a crude estimate of the thermic effect of food). Active energy is broadly the activity when heart rate is elevated or you specifically add in exercise.

  20. Its pretty useless to assume that the term resting calories means the same thing as basal metabolic rate. Apple watch appears to captures both the basal (as shown by their sleep values which are crudely identical across the night, and then during the day it is also capturing some of the activity (which could be thought of as a combination of the Non-exercise activity thermogenesis (neat) plus likely a crude estimate of the thermic effect of food). Active energy is broadly the activity when heart rate is elevated or you specifically add in exercise.

  21. BMR(basal metabolic rate) is different from RMR (resting metabolic rate).
    You can check BMR a few minutes after waking up while in bed.
    You can check RMR while sitting. My BMR heartrate is usually 60. My ‘resting’ heartrate is usually 80-90.
    Total calorie expenditure for the day is called TDEE.

  22. BMR(basal metabolic rate) is different from RMR (resting metabolic rate).
    You can check BMR a few minutes after waking up while in bed.
    You can check RMR while sitting. My BMR heartrate is usually 60. My ‘resting’ heartrate is usually 80-90.
    Total calorie expenditure for the day is called TDEE.

  23. Based on apples description of what resting energy is in. The health app, it sounds like it is not traditional BMR, it sounds like they are just estimating non high activity calories burned based on heart rate. So this would be any activity not strenuous enough for Apple Watch to classify it as active heart rate. So I believe it varies if you are standing vs sitting. But again, just a guess based on the way the health app describes resting energy.

  24. Based on apples description of what resting energy is in. The health app, it sounds like it is not traditional BMR, it sounds like they are just estimating non high activity calories burned based on heart rate. So this would be any activity not strenuous enough for Apple Watch to classify it as active heart rate. So I believe it varies if you are standing vs sitting. But again, just a guess based on the way the health app describes resting energy.

  25. Your resting heart rate changes with After Burn effect…this is 10-24 hours after strenuous activity, your resting heart rate will be slightly more than normal. Sounds like you need some fitness and health advice instead of blaming the watch.

  26. Your resting heart rate changes with After Burn effect…this is 10-24 hours after strenuous activity, your resting heart rate will be slightly more than normal. Sounds like you need some fitness and health advice instead of blaming the watch.

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