What's the difference between BMR and TDEE?

BMR is what you burn at complete rest. TDEE, total daily energy expenditure, adds activity on top. A sedentary person's TDEE is about BMR × 1.2, a very active person's about BMR × 1.725.

Should I eat less than my BMR to lose weight?

Generally no. Eat below your TDEE, not your BMR. Going under BMR for long periods makes it hard to get enough nutrients and is best done only under medical supervision.

Does muscle really raise BMR?

Yes, modestly. Muscle burns more energy at rest than fat, so building muscle raises BMR a little, and keeping it as you age slows the natural decline.

Why do the three formulas give different answers?

They were fitted to different groups of people and use different inputs. The spread between them is a reminder that any BMR figure is an estimate.

BMR Calculator: Basal Metabolic Rate

Your BMR is the energy your body burns at complete rest. By the Mifflin-St Jeor equation, a 30-year-old woman who is 170 cm and 70 kg burns about 1,452 calories a day before any movement: 10 × 70 + 6.25 × 170 − 5 × 30 − 161.

Sex (used by the formula)

Age (15–100)

years

Height

Weight

Body fat (optional, for Katch-McArdle)

BMR (Mifflin-St Jeor)

1,452 kcal

Harris-Benedict

1,492 kcal

Daily calories by activity level

SedentaryDesk job, little or no exercise	× 1.2	1,742 kcal
Lightly activeLight exercise 1–3 days a week	× 1.375	1,996 kcal
Moderately activeExercise 3–5 days a week	× 1.55	2,250 kcal
Very activeHard exercise 6–7 days a week	× 1.725	2,504 kcal
Extra activeVery hard exercise or a physical job	× 1.9	2,758 kcal

Show the math

1
Mifflin-St Jeor (recommended)
10 × 70 + 6.25 × 170 − 5 × 30 − 161 = 1,452
Published in 1990, it's the most accurate of the standard equations for most adults and the one dietitians use most.
= 1,452 kcal/day

Read the steps as text

Mifflin-St Jeor (recommended). 10 × 70 + 6.25 × 170 − 5 × 30 − 161 = 1,452 Published in 1990, it's the most accurate of the standard equations for most adults and the one dietitians use most.
Revised Harris-Benedict. 447.593 + 9.247 × 70 + 3.098 × 170 − 4.330 × 30 = 1,492 The 1984 revision of the original 1919 equation. It tends to come out slightly higher than Mifflin-St Jeor.
From BMR to daily calories. 1,452 × 1.2 (sedentary) = 1,742 · × 1.55 (moderately active) = 2,250 BMR is what you burn at complete rest. Multiplying by an activity factor estimates your total daily energy use (TDEE).

What BMR measures

Basal metabolic rate is the energy your body needs just to stay alive at rest: breathing, circulating blood, keeping warm and repairing cells. For most people it's 60 to 70% of all the calories they burn in a day, more than exercise and digestion combined.

BMR depends mainly on your size and how much of you is muscle, which is why bigger and more muscular people burn more. It also falls slowly with age. Multiplying it by an activity factor gives your total daily energy expenditure, the calories that keep your weight steady.

Which formula to trust

Mifflin-St Jeor (1990) is the most accurate of the common equations for most adults and is the default here. The revised Harris-Benedict equation (1984) usually comes out a little higher. Both use weight, height, age and sex.

Katch-McArdle uses lean body mass instead, so it needs your body fat percentage. It's often the best choice for lean or very muscular people, whose muscle the other formulas underestimate, but only if your body fat estimate is reasonably accurate. All three are estimates within about 10% for most people.

Frequently asked questions

What's the difference between BMR and TDEE?: BMR is what you burn at complete rest. TDEE, total daily energy expenditure, adds activity on top. A sedentary person's TDEE is about BMR × 1.2, a very active person's about BMR × 1.725.
Should I eat less than my BMR to lose weight?: Generally no. Eat below your TDEE, not your BMR. Going under BMR for long periods makes it hard to get enough nutrients and is best done only under medical supervision.
Does muscle really raise BMR?: Yes, modestly. Muscle burns more energy at rest than fat, so building muscle raises BMR a little, and keeping it as you age slows the natural decline.
Why do the three formulas give different answers?: They were fitted to different groups of people and use different inputs. The spread between them is a reminder that any BMR figure is an estimate.