Daily calorie calculator

How to use the calculator

1. Choose your sex — the equation differs for men and women.
2. Enter age (full years), height in centimetres and weight in kilograms.
3. Choose the activity level you actually maintain, not the one you plan to reach.
4. Choose a goal — weight loss, maintenance or mass gain. The result shows all three references, with the block for the chosen goal highlighted.
5. Press "Calculate" and take the range, not a single number.

The entered parameters are saved only in your browser: on your next visit the form fills them in automatically, while the calculated calories are not stored anywhere.

Where the formula comes from

Basal metabolism (resting energy) is computed with the Mifflin-St Jeor equation (Am J Clin Nutr, 1990): 10 × weight + 6.25 × height − 5 × age, plus 5 for men and minus 161 for women. Daily needs (maintenance) are the basal metabolism multiplied by an activity coefficient: from 1.2 (sedentary) to 1.9 (physical work or two sessions a day).

The calculator shows three references: maintenance, loss and gain. Loss is maintenance minus 20 % (a moderate deficit), gain is plus 20 % (a moderate surplus). Each reference has its own ±10 % range. A population formula describes an "average" person: two people with the same parameters can differ more in their real needs, so a single number would create false confidence.

Assumptions

• The input is ordinary publicly available parameters; body composition (the share of muscle and fat) and health status are not accounted for.
• The activity coefficient is one value for the whole training week and is chosen by the user.
• The formula was validated on adults: age 18–80, height 120–220 cm, weight 35–200 kg — outside those limits the tool does not calculate and suggests seeing a specialist.

How to check it by hand

Example: man, 30 years old, height 178 cm, weight 80 kg, moderate activity (training 3–5 days a week, coefficient 1.55).

1. Basal metabolism: 10 × 80 + 6.25 × 178 − 5 × 30 + 5 = 800 + 1112.5 − 150 + 5 = 1767.5 kcal.
2. Maintenance: 1767.5 × 1.55 ≈ 2739.6 kcal; a ±10 % range is roughly 2466–3014 kcal.
3. For weight loss (−20 %): 2739.6 × 0.8 ≈ 2192 kcal; a ±10 % range is roughly 1973–2411 kcal.
4. For mass gain (+20 %): 2739.6 × 1.2 ≈ 3288 kcal; a ±10 % range is roughly 2959–3616 kcal.

How to adjust from what you observe

A range is a starting point; after that, facts decide. Assess progress and recalculate the reference after 2–4 weeks by the actual change in weight:

1. Start from the middle of the range for your chosen goal and keep your usual nutrition for 2–4 weeks without abruptly changing your activity level.
2. Weigh yourself at the same time of day and look at the trend over 2–4 weeks, not individual days: weight fluctuates because of water, salt and gut contents.
3. If weight changes faster than planned, raise calories by a small step (for example 5–10 % of the range); if it does not change at all, lower them by the same step. After 2–4 weeks repeat the assessment with the new weight: the calculator recalculates all three references.
4. How you feel, your sleep and how well you tolerate training matter more than the number: if you feel weak and your working weights drop, go back to the previous step and check your activity level.

Limitations

• This is an estimated calculation, not a medical prescription and not a meal plan.
• The formula does not account for body composition; with noticeable muscle mass the real need can be above the estimate.
• The activity coefficient is approximate: for a mixed week take the nearest lower level.
• The input boundaries (18–80 years, 120–220 cm, 35–200 kg) are the limits of the equation's validation on adults, not a medical assessment.
• For illness, pregnancy or eating disorders, see a doctor or dietitian (see the warning at the top of the page).
• Cheap kitchen scales and "average" portions in your records add their own error: compare the weight trend, not one-off measurements.