How this calculator works

The calculator uses the Mifflin-St Jeor equation to estimate your basal metabolic rate (BMR) — the energy your body burns at complete rest. It then multiplies BMR by an activity factor to give your total daily energy expenditure (TDEE). Finally, it applies your chosen goal multiplier to set a calorie target for fat loss, maintenance, or lean gain.

Macros are split protein-first: 1.8 g per kg of body weight for protein, 25 % of target calories from fat, and the remainder from carbohydrates. This split suits most adults who resistance train. If you do not train, a lower protein target (around 1.2 g/kg) is fine.

Mifflin-St Jeor formula

The maths

Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5

Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

Prefer not to say: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 78 (midpoint)

TDEE = BMR × activity multiplier

Activity multipliers — pick honestly

What to do with the result

Use the target number as a starting budget for the next two to three weeks. Weigh yourself under the same conditions each morning and track the weekly average. If weight moves in the right direction at roughly 0.5 to 1 % of body weight per week, the target is working. If not, adjust by 100 to 150 kcal and re-test.

Do not chase precision. The calculator gives a sensible starting point — your body provides the feedback loop.

FAQ

How accurate is a TDEE calculator?
Any formula-based TDEE estimate carries roughly ±10-15 % error. The Mifflin-St Jeor equation is the most validated for adults, but individual metabolism, non-exercise activity thermogenesis (NEAT), and muscle mass all shift the real number. Treat the output as a starting point and adjust after two to three weeks based on actual weight change.
Which activity multiplier should I pick?
Most people with desk jobs who exercise three to four times a week sit between lightly active and moderately active. If in doubt, choose the lower option. Overestimating activity is the most common reason calorie targets come out too high.
Why is a woman's BMR lower than a man's at the same weight?
On average, women carry a higher proportion of body fat and less lean mass than men at the same scale weight. Because muscle tissue is more metabolically active than fat tissue, men tend to burn more energy at rest. The Mifflin-St Jeor formula accounts for this with a sex-specific constant: +5 for men, −161 for women.