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BMR & TDEE Calculator · Mifflin-St Jeor + Harris-Benedict · 5 Activity Levels

Enter gender, age, height, weight to get Basal Metabolic Rate (BMR) instantly and TDEE across 5 activity levels, plus cut / maintain / bulk calorie targets. Switch between Mifflin-St Jeor (recommended) and Harris-Benedict formulas. Fully local.

Overview

BMR is the calories you'd burn doing absolutely nothing. This tool supports two leading formulas: Mifflin-St Jeor (1990, modern gold standard, <10% error) and Harris-Benedict (1984 revised). TDEE = BMR × activity (5 levels: 1.2 / 1.375 / 1.55 / 1.725 / 1.9). Output cut/maintain/bulk calorie targets. All local.

How to use

  1. Pick gender (significantly affects formula).
  2. Enter age (years), height (cm), weight (kg).
  3. Default formula is Mifflin-St Jeor; switch to Harris-Benedict for comparison.
  4. Choose activity level from 5 presets.
  5. Panel shows BMR + TDEE + 5-level activity table + cut/maintain/bulk targets.

Formula

Mifflin-St Jeor (1990, recommended):
  Male:   10·W + 6.25·H − 5·A + 5
  Female: 10·W + 6.25·H − 5·A − 161
Harris-Benedict (1984 revised):
  Male:   88.362 + 13.397·W + 4.799·H − 5.677·A
  Female: 447.593 + 9.247·W + 3.098·H − 4.330·A
TDEE = BMR × activity (1.2 / 1.375 / 1.55 / 1.725 / 1.9)
Cut/Maintain/Bulk = TDEE ∓ 500 / = / + 500.

Common scenarios

30yo male · 175cm · 70kg · light

Mifflin BMR ≈ 1649, TDEE(1.375) ≈ 2267. Cut 1767 / Maintain 2267 / Bulk 2767.

30yo female · 165cm · 55kg · sedentary

Mifflin BMR ≈ 1270, TDEE(1.2) ≈ 1524. Cut floored at 1000. Be careful with extreme cuts.

Mifflin vs Harris

For the 30yo male above, the two differ by ~1.3%. Harris overestimates at BMI > 30; Mifflin is today's gold standard.

FAQ

Mifflin or Harris — which is more accurate?

Mifflin-St Jeor has the lowest average error (<5%) on general adults and is recommended by ADA / ACSM since 2005. It outperforms Harris at extreme BMIs. Tool defaults to Mifflin.

Why not eat as little as possible for fat loss?

Too-low calories (esp. <BMR chronically) trigger metabolic adaptation: lower RMR, thyroid, muscle loss. Stick to 300-700 kcal deficit (15-25% of TDEE). Tool floors cut at 1000 kcal.

How do I pick the right activity level?

Most people overestimate activity. An office worker who hits the gym 2x/week is "light" (1.375), not moderate. Only 3-5 intense sessions/week = 1.55. Start conservative, adjust after 2 weeks of tracking weight.

Can I compare BMR with my friend / family?

Raw BMR comparison is weak because it depends heavily on mass. BMR-to-lean-mass ratio is more meaningful; direct indirect calorimetry is the gold standard for apples-to-apples.

Is it suitable for pregnant, breastfeeding, elderly, or children?

Not recommended. Formulas are built on healthy 18-65 adults. Pregnancy / lactation need extra 300-500 kcal; elderly and kids have distinct metabolism. Consult a dietitian.

Is the data uploaded?

No — everything runs locally, nothing leaves your device.

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