# Heart rate monitors and calories **URL:** \ **Category:** Factual Questions\ **Created:** [October 19, 2010, 9:45pm UTC](https://boards.straightdope.com/t/heart-rate-monitors-and-calories/557707 "2010-10-19T21:45:56Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [October 19, 2010, 9:45pm UTC](https://boards.straightdope.com/t/heart-rate-monitors-and-calories/557707/1 "2010-10-19T21:45:56Z")
How accurate are the calories reported on heart rate monitors? The one I have knows your weight and heart rate over time. It also may use a measurement of resting heart rate as well but I am not sure about the last. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [October 19, 2010, 10:37pm UTC](https://boards.straightdope.com/t/heart-rate-monitors-and-calories/557707/2 "2010-10-19T22:37:17Z")
Not accurate at all. There is simply not enough data for the device to make any accurate measurement of calories expended. I have a Garmin 305, which I use on bike rides that knows my weight, my heart rate, my speed and distance, and elevation loss/gain. Even with all that data, it is inaccurate - a mountain bike ride that has the same percieved effort as a road bike ride will show less calories burned for the mountain bike ride (presumably because of the lower speed and distance, but I can tell the two rides are roughly the same effort). A calibrated power meter is what would be accurate. These are available for bicycles but they are not cheap. I’m not sure if they exist for other activities. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [October 20, 2010, 11:05am UTC](https://boards.straightdope.com/t/heart-rate-monitors-and-calories/557707/3 "2010-10-20T11:05:10Z")
I’m with **Dag** - there are too many additional variables. However, it appears that Polar are the leaders at determining calories expended from heartrate - the latest Garmin GPS training devices all use licensed technology from Polar to determine calorie expenditure from heartrate and GPS information. Si ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 20, 2010, 3:48pm UTC](https://boards.straightdope.com/t/heart-rate-monitors-and-calories/557707/4 "2010-10-20T15:48:57Z")
It’s a good ballpark estimate.