Your Power Meter directly measures the energy through the bike, and can be transferred into Kilojoules KJ, these can be converted to Calories directly as the ratio is 1:1. However the body is not efficient; using only 25% of your calories, the rest is lost as heat leaving the body. Therefore it is considered that the Calories burned are within 5% accuracy from your Power Meter. So 300KJ’s of workout equates to 300 Calories.

Within this, bear in mind that if you are working in Zone 5 (VO2 Max) and above, with short recovery intervals, like sprints, that you won’t end up with a high KJ expenditure. The most obvious solution to lose weight is best achieved in Zone 2, which is associated with endurance work. 

For a sedentary Man the calories needed a day are about 1800, for a sedentary woman it’s roughly  1400 calories. The average calories for a male cyclist is 2400-2700, for a female cyclist it’s 2000-2400. So it is healthy to eat to fuel the exercise you’re doing or you’ll burn out, and also fuel the recovery or you’ll get ill – mince pies are go!




% of FTP


Physiological cost




All day pace

If your goal is to maximise your body’s ability to burn fat as a fuel this is the zone for you.