Calorie Calculator (BMR & TDEE)
Enter your age, height, weight and activity level to get your basal metabolic rate and total daily calorie needs — with targets for losing or gaining weight. All figures use the Mifflin-St Jeor equation, and imperial entries in stones and feet are converted for you.
How it works
Your basal metabolic rate (BMR) — the energy your body burns at complete rest — is calculated with the Mifflin-St Jeor equation: for men 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women the same with −161 instead of +5. It is the most accurate practical formula in the nutrition literature.
Total daily energy expenditure (TDEE) multiplies BMR by an activity factor: sedentary 1.2 · lightly active 1.375 · moderately active 1.55 · very active 1.725 · athlete 1.9.
Worked example: a 40-year-old woman, 165 cm and 70 kg, has a BMR of 10 × 70 + 6.25 × 165 − 5 × 40 − 161 ≈ 1,370 kcal. If she is moderately active (multiplier 1.55) her TDEE is about 2,124 kcal a day, and a 500-calorie deficit puts her weight-loss target near 1,624 kcal — on pace for roughly 1lb a week.
The single biggest source of error is the activity multiplier: the gap between sedentary (1.2) and athlete (1.9) is nearly 60% of BMR, so overstating your activity by even one level can inflate your target by several hundred calories a day. If results stall, suspect the multiplier before suspecting the formula.
The result gives three numbers: BMR (the floor — what your body uses at complete rest), TDEE (your maintenance intake), and targets 300–500 kcal either side of maintenance for steady loss or gain. It is an estimate built from age, sex, height and weight alone; it cannot see body composition or individual metabolic variation, so treat the output as a starting point to be calibrated against your actual weight change over a few weeks.
To lose weight steadily, aim for 300–500 calories below TDEE (roughly 0.5–1lb a week); to gain, 300–500 above. Imperial entries (stone/lb, ft/in) are converted automatically. The NHS reference intake — 2,500 kcal for men, 2,000 for women — is a population average for food labelling, not a personal target: your own number, computed from your own measurements, can sit hundreds of calories either side of it.
FAQ
How many calories should I eat a day?
It depends on your size, age, sex and activity. A 30-year-old man of 5ft 9in and 12st 8lb with a desk job needs around 2,100 kcal a day; the same man training 3–5 times a week needs about 2,700. The familiar 2,000/2,500 figures on food labels are population averages — compute your own number and adjust based on how your weight actually responds over a few weeks.
What is the difference between BMR and TDEE?
BMR is what your body burns doing nothing — keeping organs running, roughly 1,400–1,900 kcal for most adults. TDEE adds everything else: daily movement, work and exercise, via the activity multiplier. Diet targets should be set against TDEE, not BMR; eating below BMR for long periods is neither necessary nor advisable for most people.
How big a deficit do I need to lose a pound a week?
About 500 kcal a day — a pound of body fat stores roughly 3,500 kcal, so a daily 500-calorie deficit adds up to one pound per week. In practice weight loss is rarely perfectly linear (water weight, adaptation), so treat the arithmetic as a starting point and adjust every few weeks based on real results. The NHS recommends losing no more than 1–2lb a week.
Which activity level should I choose?
Pick the level that matches your whole week, not your best day: sedentary (desk job, ×1.2), lightly active (×1.375), moderately active (training 3–5 times a week, ×1.55), very active (×1.725) or athlete (×1.9). If you are genuinely unsure, choose the lower option — an overstated multiplier is the most common reason a calculated target fails to produce results.
How many calories should I eat to gain weight?
Aim for 300–500 kcal above your TDEE. Using the worked example above (TDEE ≈ 2,124 kcal), that means roughly 2,400–2,600 kcal a day. As with losing weight, progress is rarely perfectly linear, so weigh in over several weeks and nudge the surplus up or down based on the trend rather than any single day's reading.
Is my BMR the number of calories I should eat?
No — BMR is the energy your body burns at complete rest and acts as a reference floor, not a target. Set your intake against TDEE, which adds daily movement and exercise on top. Eating below BMR for long periods is neither necessary nor advisable for most people; even a full 500-calorie deficit normally leaves your target comfortably above BMR, as the worked example shows (1,624 versus 1,370 kcal).
Do imperial units change the result?
No — entries in stones and pounds or feet and inches are converted to kilograms and centimetres before the equation runs, so 12st 8lb and 80 kg produce the same answer. Use whichever units you know your measurements in most accurately; precision in the inputs matters more than the system they are entered in.