Calories burned from heart rate
·
Heart rate is the best signal a watch has for how hard you worked. Here is what it can and cannot tell you about calories.
How the number is worked out
The calculator uses the Keytel equation, published in 2005 in the Journal of Sports Sciences, which relates energy expenditure to heart rate, body mass, age and sex. It is the same family of equation that sits inside most fitness watches.
Two things follow from that. It works well for steady cardio in the range where heart rate tracks effort, roughly 90 to 150 beats per minute for most people. And it works badly whenever your heart rate rises for a reason other than effort.
When heart rate lies about calories
Caffeine, heat, dehydration, stress and poor sleep all push your heart rate up without any extra work being done. Weight training does the opposite: heavy sets burn real energy while your average heart rate stays modest, so the equation underestimates you.
Wrist sensors add their own error. They read light through the skin, and they struggle with cold hands, tattoos and anything involving grip, which is why rowing and cycling numbers are often the least reliable.
What the margin means
The range under the result is not decoration. Two people with the same weight, age and heart rate can differ by ten to fifteen percent in real expenditure, because fitness changes how much work a given heart rate represents. A trained runner at 140 beats per minute is doing far more than an untrained one.
Use the number to compare your own sessions week to week. Do not use it to justify a second dessert, because the error on one workout is larger than most desserts.
Stop doing this by hand
This tells you what you burned. Kalixo tells you what you ate, from a photo of the plate.
Get Kalixo free on the App StoreQuestions people actually ask
Is heart rate a better calorie estimate than step count?
For steady cardio, yes. Steps say nothing about intensity: an easy walk and a hill sprint can produce a similar step count with very different energy costs. For weight training or anything stop-and-start, neither method is good.
Why do my watch and this calculator disagree?
Your watch adds data this page does not have, mainly your resting heart rate and your measured fitness level, and each manufacturer layers its own correction on top. A gap of ten to twenty percent between two honest estimates is normal.
Should I subtract the calories I would have burned anyway?
Strictly, yes. Sitting still for 45 minutes already costs roughly 50 to 70 calories, and that share is included in the figure above. If you are counting carefully, subtract it rather than treating the whole number as a bonus.
What heart rate should I use for the whole session?
The average for the time you were actually moving, not the peak. Using your maximum will overstate the result badly, sometimes by half.