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Katch-McArdle BMR Calculator

Estimate your BMR with the Katch-McArdle formula from lean body mass or body fat %, then get your TDEE at five activity levels.

Katch-McArdle inputs

Basal metabolic rate (Katch-McArdle)

1,781 calories/day

The energy your body burns at complete rest, driven entirely by 144 lb of lean mass.

Maintenance calories (TDEE)

2,761 calories/day

BMR times the moderately active (moderate exercise 3 to 5 days/week) factor of 1.55.

Lean mass

144 lb

Fat mass

35.9 lb

Body fat

20.0%

TDEE at every activity level

  • Sedentary (little or no exercise) (x1.2)2,137
  • Lightly active (light exercise 1 to 3 days/week) (x1.375)2,449
  • Moderately active (moderate exercise 3 to 5 days/week) (x1.55)2,761
  • Very active (hard exercise 6 to 7 days/week) (x1.725)3,072
  • Extra active (hard daily exercise or a physical job) (x1.9)3,384

Calorie targets at this activity level

Lose 1 lb/week

2,261

Lose 0.5 lb/week

2,511

Gain 0.5 lb/week

3,011

Gain 1 lb/week

3,261

Targets adjust the selected TDEE by 250 or 500 calories per day. Eating well below your BMR for long stretches is not advised.

Frequently Asked Questions about the Katch-McArdle BMR Calculator

What is the Katch-McArdle BMR formula?
The Katch-McArdle equation estimates your basal metabolic rate as 370 plus 21.6 times your lean body mass in kilograms. Because it is built on lean mass alone, it ignores age, height, and sex. That makes it well suited to people who know their body composition, especially lean and athletic individuals.
How do you get lean body mass from body fat percentage?
Your lean body mass is your total weight minus your fat mass. The calculator computes it as weight times (1 minus body fat % divided by 100). For example, at 80 kg and 20% body fat, your lean mass is 64 kg and your fat mass is 16 kg.
How is TDEE calculated from BMR?
Total daily energy expenditure multiplies your BMR by an activity factor. This calculator uses the standard factors: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, and 1.9 for extra active. You see your TDEE at all five levels so you can compare them side by side.
When should I use Katch-McArdle instead of Mifflin-St Jeor?
Use Katch-McArdle when you have a reliable body fat or lean mass measurement, such as a DEXA scan or skinfold test. Because it keys off lean mass rather than total weight, it tends to be more accurate for muscular or very lean people. If you do not know your body composition, the Mifflin-St Jeor formula is usually the safer default.
Should I enter body fat percentage or lean body mass?
Pick whichever you can measure most accurately. If you already know your lean body mass from a body scan, enter it directly in lean-mass mode. Otherwise enter your body weight and body fat percentage, and the calculator derives your lean mass for you.
Is this a substitute for medical advice?
No. BMR and TDEE figures are estimates for education and general planning, not medical or clinical guidance. Calorie needs vary with genetics, health conditions, and medication, so check with a doctor or registered dietitian before making large changes to your diet.

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