Calorie Needs Calculator
Work out your BMR and total daily energy needs from age, sex, height, weight, and activity level — using the Mifflin-St Jeor equation.
At rest your body burns about 1,699 kcal a day (BMR). Adjusting for your activity level, your total daily energy expenditure is 2,633 kcal — the calories you'd eat to maintain weight.
Daily calories by goal
Results update as you type. The Mifflin-St Jeor equation is the most accurate widely used formula at population level, but individual energy expenditure varies — treat the numbers as a starting estimate, not a prescription.
Formula
The Mifflin-St Jeor BMR equation:
BMR = 10·kg + 6.25·cm − 5·age + s, where
s = +5 for males, s = −161 for females. TDEE is BMR multiplied by
an activity factor (sedentary 1.2 → extra-active 1.9). Goal calories are TDEE shifted by
±500 or ±1000 — the latter giving roughly 1 kg of weight change per week (3,500 kcal ≈ 0.45
kg of fat).
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Frequently asked questions
What's the difference between BMR and TDEE?▾
BMR (basal metabolic rate) is what your body burns at complete rest — keeping organs running, body temperature stable, basic biological processes going. It's roughly 60–75% of total energy expenditure for a sedentary person, less for an active one. TDEE (total daily energy expenditure) is BMR plus everything else: walking, working, exercise, fidgeting, digestion. TDEE is the figure you'd eat to maintain weight.
How accurate is the Mifflin-St Jeor formula?▾
It's the most accurate widely used BMR equation at population level — the American Dietetic Association reviewed several formulas in 2005 and rated Mifflin-St Jeor most accurate for healthy adults. Individual variation is still ±10% or so: two people with identical height/weight/age can have meaningfully different metabolic rates due to body composition (muscle burns more than fat) and genetics. Treat the result as a starting estimate, not a precise prescription.
Why does the calculator need my sex?▾
Because the Mifflin-St Jeor equation has a sex-specific constant (+5 for males, −161 for females) that captures the average difference in body composition. The formula isn't ideal for people whose body composition doesn't match the binary assumption (transgender people on hormone therapy, athletes with very high muscle mass) — in those cases, treat the number as a starting point and adjust based on how your weight responds over a few weeks.
What activity level should I pick?▾
Be honest, and lean conservative. 'Sedentary' fits desk work with no real exercise (most office jobs). 'Lightly active' is 1–3 light gym sessions/week or daily walking. 'Moderately active' is 3–5 proper sessions a week. 'Very active' is 6–7 hard sessions OR a physically demanding job. 'Extra active' is athletes and people doing both daily training AND a physical job. Most people overestimate their activity — start one notch lower than feels right.
Why is the deficit floor 1,200 kcal?▾
Below 1,200 kcal/day for women (~1,500 for men) it becomes hard to hit basic vitamin and mineral targets without supplementation, and metabolism downregulates faster, making the deficit progressively harder to sustain. The NHS recommends slow steady deficits (250–500 kcal/day, half a kilo a week) over rapid loss for most people. Aggressive deficits work briefly but rebound is common — and unsupervised very-low-calorie diets carry medical risks including gallstones, electrolyte disturbance, and muscle loss.
Should I cut by 1,000 kcal/day to lose weight fast?▾
Probably not. A 1,000 kcal/day deficit theoretically gives ~1 kg/week loss but is hard to sustain, often produces fatigue and food preoccupation, and risks the calorie floor. The NHS, BDA, and most evidence-based weight services recommend 500 kcal/day deficits as the default, accepting slower loss in exchange for adherence and preserving lean mass. The numbers in this calculator are mathematical, not endorsements.