Calorie calculator: how many calories you need per day
Enter your sex, age, height and weight — the calculator estimates your basal metabolic rate, maintenance calories and a daily calorie goal, plus protein, fat, carbs, water and fiber. It uses the same math as the Fitaline app.
How the calculation works
- Basal metabolic rate (BMR) is the energy your body uses at rest: breathing, heart and brain function, keeping warm. It is estimated with the Mifflin–St Jeor equation:
men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 - Maintenance calories (TDEE) are your BMR multiplied by an activity factor: 1.2 — sedentary, 1.375 — lightly active, 1.55 — workouts 3–5 times a week, 1.725 — hard physical work. It is a reference number: roughly how much keeps your weight stable.
- The calorie goal is based on your BMR. To lose weight — a 10, 15 or 20 % deficit (gentle, moderate or fast pace); to build muscle — a 5, 10 or 15 % surplus; to maintain — the BMR itself. The goal never goes below 1,200 kcal.
- Workouts are added on top. Calories burned in workouts and walks are added to the goal on the day you log them. That way activity is never counted twice, and you don’t overeat on rest days.
- Macros, fiber and water. Protein, fat and carbs are shares of calories for your goal: 30/25/45 % when losing weight, 30/20/50 % when gaining, 25/20/55 % when maintaining. Fiber is about 14 g per 1,000 kcal, water 35 ml per kilogram of body weight (1.5 to 4 L).
A worked example
A man, 30 years old, 180 cm (5′11″), 85 kg (187 lb), working out 3–5 times a week, wants to lose weight at a moderate pace.
| Value | Calculation | Result |
|---|---|---|
| BMR | 10 × 85 + 6.25 × 180 − 5 × 30 + 5 | 1,830 kcal |
| Maintenance | 1,830 × 1.55 | 2,837 kcal |
| Goal on a rest day | 1,830 × (1 − 0.15) | 1,556 kcal |
| Goal on a day with a 450 kcal workout | 1,556 + 450 | 2,006 kcal |
| Protein / fat / carbs | 30 / 25 / 45 % of 1,556 kcal | 117 / 43 / 175 g |
| Water | 35 ml × 85 | ≈ 3 L |
Why the goal starts from BMR
Classic calculators multiply your BMR by an activity factor and subtract a deficit. But the factor is an average: on rest days it overestimates your needs, and on hard training days it underestimates them. Fitaline starts from your BMR and adds activity as it happens — from your workout log, steps and the afterburn after strength training. If you don’t log workouts, use maintenance calories and subtract 10–20 % to lose weight.
How to use the result
- It is a starting point, not an exact number: for an individual the equation can be off by about 10 %. Watch your weight for 2–3 weeks and adjust the goal.
- Lose 0.5–1 % of your body weight per week so that you lose fat, not muscle. More in “How to lose weight”.
- When building muscle, gain no more than 0.25–0.5 % of your body weight per week — see “How to build muscle”.
- Don’t go below 1,200 kcal without medical supervision.
- Tracking calories every day is easier in a food diary: Fitaline compares what you ate with your goal, adds workouts and updates your target when your weight changes.
Frequently asked questions
How accurate is a calorie calculator?
The Mifflin–St Jeor equation is one of the most accurate for healthy adults, but it can still be off by about 10 % for an individual. Use the result as a starting point and adjust it based on how your weight changes over 2–3 weeks.
How many calories should I eat to lose weight?
A deficit of 10–20 % below your needs is usually enough. A harsher deficit speeds up muscle loss, increases hunger and raises the risk of giving up.
Why not eat less than 1,200 calories?
With very few calories it is hard to get enough protein, vitamins and minerals. Such diets are only appropriate under medical supervision.
Should I eat back my workout calories?
Yes, if your goal is based on BMR, as in Fitaline: calories burned in a workout are added to that day’s target. If you use maintenance calories with an activity factor, your workouts are already included.
What is the difference between BMR and maintenance calories?
BMR is the energy you need at complete rest. Maintenance calories also include your daily movement: they are your BMR multiplied by an activity factor.
Sources
- Mifflin M. D., St Jeor S. T., Hill L. A. et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247.
- Frankenfield D., Roth-Yousey L., Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775–789.
- Dietary Guidelines for Americans, 2020–2025 (fiber: 14 g per 1,000 kcal).
This article is for information only and is not a substitute for medical advice. If you have a medical condition, are pregnant or breastfeeding, agree your diet and exercise with a doctor.