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Mifflin-St Jeor Calculator

The Mifflin-St Jeor equation is the most accurate BMR formula for the general population. Published in 1990, it's the default formula used by registered dietitians and the American Dietetic Association.

1990

Published with representative population data — the modern clinical default.

±10%

Predicts BMR within 10% for ~82% of non-obese adults vs. indirect calorimetry.

2 constants

Sex-specific adjustment: +5 for men, −161 for women.

The formula

Men

(10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5

Women

(10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161

Worked examples

Example 1: 30-year-old man, 180 lb, 5'10"

Weight: 180 lb ÷ 2.205 = 81.6 kg
Height: 70 in × 2.54 = 178 cm
BMR = (10 × 81.6) + (6.25 × 178) − (5 × 30) + 5
BMR = 816 + 1,113 − 150 + 5

1,784calories / day

Example 2: 35-year-old woman, 140 lb, 5'5"

Weight: 140 lb ÷ 2.205 = 63.5 kg
Height: 65 in × 2.54 = 165 cm
BMR = (10 × 63.5) + (6.25 × 165) − (5 × 35) − 161
BMR = 635 + 1,031 − 175 − 161

1,330calories / day

From BMR to TDEE

BMR alone is not your daily calorie target — it's just the resting baseline. Multiply by your PAL (Physical Activity Level) to get TDEE:

Total daily energy

TDEE = BMR × PAL

Physical activity level

PAL = Σ(MET_i × hours_i) / 24

PAL is the weighted average of your day's MET (Metabolic Equivalent of Task) values. Common references:

Activity	MET
Sleep	1.0
Sedentary (desk work, watching TV)	1.3
Light activity (walking, chores)	3.0
Moderate (gym, jogging, sports)	6.0
Vigorous (running, HIIT)	9.0

Many online calculators use a 5-bucket dropdown (1.2 / 1.375 / 1.55 / 1.725 / 1.9) instead. It's fast but most people don't fit any bucket cleanly. FindTDEE uses the MET method to calculate a personalized PAL.

Frequently asked questions

Is Mifflin-St Jeor the most accurate BMR formula?

For the general population, yes. Studies comparing it against indirect calorimetry (the gold standard) show Mifflin-St Jeor predicts BMR within 10% for ~82% of non-obese adults. Harris-Benedict is older and overestimates by ~5%. Katch-McArdle is more accurate if you know your body fat percentage, since it works from lean body mass instead.

Does Mifflin-St Jeor work for athletes?

It works, but underestimates slightly because it doesn't account for body composition. Lean, muscular athletes are better served by the Katch-McArdle formula, which uses lean body mass directly.

Why does the formula have different versions for men and women?

Men and women have different body compositions on average — men carry more lean mass at the same body weight, which burns more calories at rest. The +5 / −161 constants in the formula correct for this difference.

What's the difference between Mifflin-St Jeor and Harris-Benedict?

Both estimate BMR from age, weight, height, and sex. Harris-Benedict was published in 1919 (revised 1984) using older population data and tends to overestimate modern BMR by 5%. Mifflin-St Jeor was published in 1990 with more representative data and is now the default in clinical and sports nutrition settings.

How does BMR relate to TDEE?

BMR is the calories you'd burn lying motionless for 24 hours. TDEE is BMR multiplied by your PAL (Physical Activity Level), which is the weighted average of MET values across your 24-hour day. TDEE is what you actually burn in a real day, and the number you set calorie goals from.

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