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Calorie calculator
Estimate your basal metabolic rate, your total daily energy expenditure and a daily calorie target — free, in your browser, without an account.
Estimate your energy needs. A starting point — adjust after 2–4 weeks.
In the myPeptides app you can save the result as your daily target and keep it next to your weight and intake history.
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How this calculator works
Without a body fat percentage the calculator uses the Mifflin-St Jeor equation, the formula most nutrition guidelines fall back on. It estimates your basal metabolic rate — the energy your body burns at complete rest — from weight, height, age and sex: 10 × kg + 6.25 × cm − 5 × age, plus 5 for men and minus 161 for women.
If you enter a body fat percentage the calculator switches to Katch-McArdle. That equation ignores height, age and sex and works from lean body mass alone: 370 + 21.6 × lean mass in kg. It is the better estimate when your body fat has actually been measured, and the worse one when the number is a guess.
The basal rate is then multiplied by an activity factor. The result is your total daily energy expenditure: everything you burn on a normal day, training, work and everyday movement included.
| Activity level | Factor | Roughly what that means |
|---|---|---|
| Sedentary | × 1.2 | Desk job, little or no exercise. |
| Lightly active | × 1.375 | Light exercise one to three days a week. |
| Moderately active | × 1.55 | Exercise three to five days a week. |
| Active | × 1.725 | Hard training six or seven days a week. |
| Very active | × 1.9 | Hard training every day, or physical work on top. |
The daily target puts your goal on top of that: 500 kcal less to lose weight, the expenditure itself to maintain, 300 kcal more to gain. Around 500 kcal a day works out at roughly half a kilo of body weight per week. If your target falls below your basal metabolic rate the calculator says so — a deficit that deep is hard to hold and rarely a good idea without supervision.
What the numbers can and cannot tell you
Every one of these formulas is a population average. Two people of the same height, weight and age can differ by several hundred calories a day, and the activity factor is the roughest part of the calculation. Treat the result as a starting point, not as a measurement.
The honest test is the scale. Eat at your target for two to four weeks, weigh yourself under the same conditions, and adjust by 100 to 200 kcal if the trend is not going where you want it to. Medication, illness, sleep and stress all shift the number, and so does losing weight itself — which is why the calculation needs repeating as your weight changes.
Frequently asked questions
How accurate is a calorie calculator?
For most people the estimate lands within about ten percent of their real needs, which is a few hundred calories a day. Accurate enough to start with, and not accurate enough to argue with the scale after a month.
Mifflin-St Jeor or Katch-McArdle?
Use Mifflin-St Jeor when you do not know your body fat percentage; it only needs weight, height, age and sex. Use Katch-McArdle when you have a measured value, because it works from lean mass and copes better with very lean or very heavy bodies. The calculator picks for you: leave the body fat field empty for Mifflin-St Jeor, fill it in for Katch-McArdle.
Which activity level fits me?
The one that matches a normal week, not your best week. Someone who trains three times a week and otherwise sits at a desk is moderately active at most. Picking one level lower and adjusting upwards later is the harmless mistake.
How large should a deficit be?
The preset is 500 kcal below your expenditure, roughly half a kilo a week. Bigger deficits cost more muscle and are harder to sustain. If the target slips below your basal metabolic rate, make it smaller or talk to a doctor or dietitian.
How often should I recalculate?
Every few kilos of weight change, or whenever your training or your job changes noticeably. A lighter body needs less energy, so a target that fit at the start of a diet is too generous ten kilos later.