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TDEE formula: how is TDEE calculated?

Reviewed 2 November 2026 · How these numbers are calculated

The classic formula is TDEE = BMR × activity factor, where the factor runs from 1.2 (sedentary) to 1.9 (extra active), and BMR usually comes from the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, + 5 for men or − 161 for women. For a 40-year-old woman of 70 kg (154 lb) and 165 cm, BMR is about 1,370 calories, and lightly active (× 1.375) gives a TDEE of about 1,880.

How to calculate TDEE

Calculating TDEE takes two steps: work out your BMR from your sex, age, height and weight, then multiply it by an activity factor for how much you move. A calculator does both at once, but the math is simple enough to do by hand.

Step 1: your BMR

Your basal metabolic rate (BMR) is what your body burns lying still all day. Three equations are in common use:

Mifflin-St Jeor (1990)
Men: 10 × kg + 6.25 × cm − 5 × age + 5
Women: 10 × kg + 6.25 × cm − 5 × age − 161

Harris-Benedict (revised by Roza and Shizgal, 1984)
Men: 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age
Women: 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age

Katch-McArdle (needs your body-fat percentage)
370 + 21.6 × lean body mass (kg)
Lean body mass = weight × (1 − body fat % ÷ 100)

Using pounds and inches? Convert first: kg = lb × 0.4536, cm = inches × 2.54. For targets by sex, see how many calories a woman should eat and how many calories a man should eat; both work from daily steps.

Step 2: multiply by your activity factor

What each level means in daily steps is on TDEE activity levels explained.

Activity factors and the TDEE they give
Activity levelFactorWoman70 kg, 40Man85 kg, 40
SedentaryDesk job, little or no exercise× 1.21,6402,120
Lightly activeLight exercise 1–3 days a week× 1.3751,8802,430
Moderately activeModerate exercise 3–5 days a week× 1.552,1202,740
Very activeHard exercise 6–7 days a week× 1.7252,3603,050
Extra activePhysical job plus hard training× 1.92,6003,360
BMR by Mifflin-St Jeor: woman 165 cm (5′5″), 1,370; man 178 cm (5′10″), 1,770.

Worked example

A 40-year-old man, 85 kg (187 lb), 178 cm (5′10″), who trains three times a week:

  1. BMR = 10 × 85 + 6.25 × 178 − 5 × 40 + 5 = 850 + 1,112.5 − 200 + 5 = 1,767.5 calories
  2. Moderately active: 1,767.5 × 1.55 = 2,740 calories a day
  3. To lose about 0.5% of his weight a week (0.43 kg), eat about 470 calories a day less: about 2,270.

The three BMR formulas compared

BMR in calories a day by each equation
PersonMifflinHarris-B.Katch
Woman, 3060 kg, 165 cm, 25% fat1,3201,3801,340
Woman, 4585 kg, 165 cm, 38% fat1,5001,5501,510
Man, 3075 kg, 178 cm, 15% fat1,7201,7801,750
Man, 50100 kg, 180 cm, 28% fat1,8802,0101,930
Harris-Benedict usually comes out highest; Katch-McArdle is lower for people with more body fat and higher for lean, muscular people.

Which formula is most accurate?

For most adults, Mifflin-St Jeor. In a systematic review it predicted resting burn within 10% for more people than the other equations, while Harris-Benedict tends to come out a little high. Katch-McArdle can be better if you know your body fat from a decent scan, because it works from lean mass: it suits muscular people the other formulas underestimate. Either way, every equation misses some individuals by 10% or more. More on how accurate TDEE calculators are and how to find your real number.

BMR vs TDEE

BMR is only the resting part. TDEE adds everything else: daily life, walking, exercise and digesting food. For most people TDEE is 1.25–1.7 times BMR. The full comparison is on BMR vs TDEE; resting burn by age and weight is on how many calories you burn doing nothing.

Why Deficitly doesn't use activity factors

The weak spot of the classic formula is the factor. "Lightly" and "moderately active" mean different things to different people, and one step between them is worth 240–310 calories a day. Deficitly builds TDEE from parts instead: BMR, plus 10% for daily life, plus your average steps (from your height and weight), plus your workouts (MET values), divided by 0.9 to add digestion. For the woman above, that gives about 1,750 calories at 3,000 steps a day, 1,890 at 8,000 and 1,990 at 12,000: your step count replaces the guess. More in maintenance calories by daily steps.

From TDEE to a weight-loss target

Eat less than your TDEE: about 7,700 calories add up to 1 kg of body fat, so a deficit of 500 a day is about 0.45 kg (1.0 lb) a week. See how many calories to eat to lose weight.

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