Cycling Calories Calculator from Power
If you ride with a power meter, your work in kilojoules is a direct measure of energy. Enter your average power and ride time to get the work done and an estimate of the calories you burned, assuming a gross efficiency of about 24% (change it if you like). It answers questions such as how many calories you burn cycling at 150 watts for 2 hours.
Updated
Report a problem
Formula
work (kJ) = average power (W) x time (s) / 1000calories burned (kcal) = work (kJ) / 4.184 / gross efficiency- At about 24% efficiency,
4.184 x 0.24 = 1.004, so kilojoules of work are approximately kilocalories burned.
The 4.184 kJ per kcal conversion is exact by definition. The efficiency is an assumption (default 24%), so the calorie figure is an estimate.
Worked example
200 W for 1 hour 30 minutes (5400 s), 24% efficiency:
- Work: 200 x 5400 / 1000 = 1080 kJ
- Calories: 1080 / 4.184 / 0.24 = 1075.5 kcal, about 717 kcal per hour
When to use it
Use it after a ride with a power meter or smart trainer, when you want to plan fuelling or log training load. Kilojoules are shown on most bike computers, so you can also type the ride duration and average watts from your own file.
Why kilojoules roughly equal calories
Human gross efficiency on a bike is about 20 to 25%. Because 1 kcal = 4.184 kJ, the two factors almost cancel, so the kilojoules of work on your head unit are close to the kilocalories you burned. At 24% efficiency the ratio is 1.004.
Common mistakes
- Using normalised power instead of average power. Work is based on the average.
- Counting coasting time as riding at your average watts. Zeros should be in the average.
- Reading the result as exact. A different efficiency changes the answer: 1,080 kJ is about 1,291 kcal at 20% and 1,033 kcal at 25%.
How it differs from nearby tools
The calories burned calculator estimates from body weight and activity type (MET values). This page uses measured power, which is usually more accurate for cycling.
Frequently asked questions
How many calories does 200 watts burn?
At 200 W you do 200 x 3600 / 1000 = 720 kJ of work in an hour. At 24% efficiency that costs 720 / 4.184 / 0.24 = 717 kcal per hour, so a 1 hour 30 minute ride burns about 1076 kcal.
Why are kilojoules about equal to kilocalories on a bike?
One kilocalorie is 4.184 kJ, and your body turns only about 24% of the energy it burns into pedal work. 4.184 x 0.24 is 1.004, so 1 kJ of work costs almost exactly 1 kcal. That is why many riders read kJ on their power meter as calories.
What efficiency should I use?
Gross efficiency in trained cyclists is commonly quoted between about 20% and 25%, and 24% is a widely used round figure. A lower value means more calories for the same work: 540 kJ at 20% is 645 kcal, against 538 kcal at 24%.
Does this include calories burned at rest?
No. The result is the energy estimated for the pedalling itself, from the work you did. It does not subtract or add your resting energy use, and it ignores coasting unless your average power already includes the zeros.
How accurate is the calorie estimate?
The kilojoule figure is exact for the power and time you enter, if the power meter is accurate. The calorie figure is an estimate that depends on the efficiency you assume, which varies from person to person by a few percentage points.
How many calories do you burn cycling at 150 watts for 2 hours?
150 W for 7,200 s is 150 x 7,200 / 1000 = 1,080 kJ of work. At 24% efficiency that is 1,080 / 4.184 / 0.24 = about 1,075 kcal, or roughly 538 kcal per hour.
How many calories is 1,000 kJ on a bike?
At 24% efficiency, 1,000 kJ of work is 1,000 / 4.184 / 0.24 = about 996 kcal. Because 4.184 x 0.24 is close to 1, kilojoules and kilocalories are nearly interchangeable.
How many calories do you burn in 1 hour at 250 watts?
250 W for 3,600 s is 900 kJ of work. At 24% efficiency that is 900 / 4.184 / 0.24 = about 896 kcal.