How much your body burns each day
A few details are enough to estimate your basal metabolic rate, your daily expenditure and the intake that matches your goal. It’s the starting point of any serious plan: without it, a nutrition recommendation is just a number picked at random.
Fill in your measurements, then press Calculate.
The calculation happens in your browser. Your measurements don’t leave your device, unless you then choose to attach them to your assessment request.
Four things worth knowing before you look at your number
- 01
Your body burns energy even when you do nothing
Breathing, keeping your heart beating, holding your temperature, running your organs: that’s your basal metabolic rate, and it accounts for most of what you burn in a day. You burn most of your calories without moving.
- 02
Your session counts for less than your day
An hour of training matters, but it isn’t doing the heavy lifting: walking, climbing stairs, standing, moving around at work often add up to more over a week. That’s why the activity level is the most important question in the calculator.
- 03
Eating less without training costs you muscle
In a deficit without training, the body draws on fat but also on muscle. And less muscle means a lower metabolism: you lose weight, then put it back on faster than before. Training is what protects your muscle while you lose.
- 04
And training without changing anything at the table isn’t enough either
What you burn in a session can be undone in a few minutes at the table. People often sum it up as “it’s fifty-fifty”: there’s no exact figure, but the idea holds. Neither one makes up for the other. What you eat decides the direction; training decides what you lose.
Going furtherThe exact formulas, the activity coefficient, and what the calculation can’t see.
No black box. You can redo the calculation by hand and land on exactly the same number.
The two formulas offered
Mifflin-St Jeor, published in 1990, is selected by default. For a man: 10 × weight in kg, plus 6.25 × height in cm, minus 5 × age, plus 5. For a woman, the same calculation, minus 161 instead of plus 5. It’s the formula nutrition bodies recommend today, because it’s the most accurate across the general population.
Harris-Benedict, in the version revised by Roza and Shizgal in 1984, is older. For a man: 88.362, plus 13.397 × weight, plus 4.799 × height, minus 5.677 × age. For a woman: 447.593, plus 9.247 × weight, plus 3.098 × height, minus 4.330 × age. It usually gives a few dozen kilocalories more.
If you’re unsure, stay with Mifflin-St Jeor. Trying both mainly shows you one thing: these are estimates, and two serious methods never land on exactly the same number.
The scenarios
Your daily expenditure is your maintenance level: eating around that figure keeps your weight stable. The scenarios apply a percentage to it, from −20% to +20%.
These are reference points, not a prescription. The right gap depends on where you’re starting from, on your goal, and on what you can sustain. That’s what we settle together at the assessment.
The activity coefficient
Your basal metabolic rate is multiplied by a coefficient running from 1.2 for a sedentary life to 1.9 for training twice a day. That coefficient covers your whole day: work, getting about, housework, not just your training sessions.
It’s the biggest source of error in the calculation, because everyone overestimates their activity. When in doubt, pick the level below the one you were going to choose.
What this number doesn’t tell you
It ignores your body composition. At the same weight, a muscular person burns more than someone who isn’t, and neither of these formulas can see that.
It also ignores your history. A body coming out of several months of restriction doesn’t burn like a body that has never dieted. That’s one of the reasons I don’t set your calorie target without having spoken to you.
Finally, this is not medical advice. In case of illness, medical treatment, pregnancy or an eating disorder, these estimates do not apply and a healthcare professional should be consulted.
Your data
Everything is worked out in your browser. Your age, your height and your weight are not sent to any server. If you click “Add to my assessment”, they are carried into the questionnaire, and only reach me if you choose to send it.