Calorie calculator
How many calories do you actually need?
Estimate what you burn in a day, then see what a deficit really looks like — including the intake floor below which a clinician would tell you to stop.
Fill in the fields above to see your estimate
These are estimates from an equation, not measurements. Real requirements vary by perhaps 10% either way, and more if you have a thyroid or metabolic condition.
How the estimate is made
The calculator uses the Mifflin-St Jeor equation to estimate your resting metabolic rate — the energy you would burn doing nothing all day — then multiplies it by an activity factor to reach your total daily expenditure. Mifflin-St Jeor is the current standard because it is more accurate than the older Harris-Benedict equation, particularly for people carrying excess weight.
An equation cannot know your body composition. Two people with identical height, weight, age and sex can differ by a few hundred calories a day.
What a deficit does and does not do
Roughly 7,700 kcal is stored in a kilo of body fat, which is where the familiar '500 kcal a day for half a kilo a week' figure comes from. It holds early on and then stops holding: as you lose weight there is less of you to maintain, so expenditure falls and the same intake becomes a smaller deficit. That is the arithmetic behind most plateaus, and it is not a failure of willpower.
Adaptive changes on top of that arithmetic are real but smaller than commonly claimed. The practical response is to recalculate as your weight changes, not to cut further and further.
Why there is a floor
Faster is not better. Below roughly 1,200 kcal a day for women and 1,500 for men it becomes difficult to meet protein and micronutrient needs, the proportion of weight lost as muscle rises, and the risk of gallstones increases with the speed of loss. Very low calorie diets exist as a medical intervention, under supervision, and are not something to improvise.
If the calculator clips your target to the floor, that is the signal to get clinical input rather than to eat less.
Protein matters more than the exact number
Adequate protein and some resistance exercise are what keep weight loss weighted toward fat rather than muscle. This matters at any rate of loss and matters more the faster it happens — which is why it is part of the clinical advice alongside any treatment, not an optional extra.
Hitting your calorie target while eating almost no protein produces a worse result at the same weight on the scale.
If the numbers are not translating into results
Plateaus, a slower response than expected, or losing weight but feeling worse are all worth clinical input. The Docalo eligibility assessment is free and takes about ten minutes; a licensed doctor reviews it and decides whether treatment is clinically appropriate.
Free assessment. Membership starts only after a clinician reviews your case.