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TDEE calculator / Katch-McArdle

Katch-McArdle Calculator

Estimate your BMR and daily calories from lean body mass. Enter your body fat percentage for a result built around your muscle, not just your weight.

3 formulas comparedMacros for every goalNo sign-up, no data stored

Your details

Sample values. Change them to yours.
Units
Sex
yrs
kg
cm
Torn between two? Pick the lower one. How to choose
%
Don't know it? Estimate it with the body fat calculator.
Macro split

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Your maintenance calories (TDEE)
—calories / day
Fill in your details to see your numbers.
—
TDEE (maintenance)
—
BMR (at rest)
—
Expected weekly change

Daily Targets

Maintain weight
Calories—
% of calories
Protein —30%
Fat —35%
Carbohydrate —35%

Formula comparison

Same inputs, three equations. Tap one to use it.

Macros at every goal

Each target gets its own grams, so you can compare goals before you start.

GoalCaloriesProteinFatCarbs
Written by AdnanUpdated Sources listed at the end

The Katch-McArdle formula

Lean body mass (kg) = weight × (1 − body fat % ÷ 100)
BMR = 370 + 21.6 × lean body mass
TDEE = BMR × activity factor

Lean body mass is everything that isn't fat: muscle, bone, organs and water. It accounts for most of the energy your body uses at rest, which is why a formula built on lean mass can track metabolism more closely than one built on total weight.

Worked example

Take an 80 kg person at 20% body fat. Their lean body mass is 80 × 0.8 = 64 kg. BMR is 370 + 21.6 × 64 = 1,752 calories. With moderate activity (× 1.55), TDEE is about 2,716 calories a day.

Now take someone of the same weight at 12% body fat. Lean mass rises to 70.4 kg and BMR to about 1,891 calories, roughly 140 more. Mifflin-St Jeor would give both people the same answer, because it only sees weight and height.

When to use Katch-McArdle

  • You are lean or muscular. Weight-based formulas tend to underestimate your needs.
  • You carry more body fat than average. Weight-based formulas tend to overestimate BMR, and lean mass gives a more grounded number.
  • You have a reliable body fat measurement. The result is only as good as that input.

If none of these apply, or your body fat figure is a guess, the main TDEE calculator with Mifflin-St Jeor is the better starting point. Both results appear side by side in the formula comparison above.

How to measure body fat

No home method is exact. What matters most is using the same method under the same conditions each time. The free body fat calculator uses the US Navy tape-measure method.

MethodHow it worksNotes
DEXA scanLow-dose X-ray of fat, lean and bone massThe most detailed option for most people. Costs money and needs a clinic.
Smart scale (BIA)A small electrical current through the bodyConvenient, but readings shift with hydration, food and time of day.
Skinfold calipersPinch measurements at set sitesCheap. Accuracy depends on the person measuring.
Tape measure (US Navy method)Neck, waist and hip measurementsFree and repeatable. A rough estimate, less reliable for very muscular people.

Frequently asked questions

What is the Katch-McArdle formula?
It estimates basal metabolic rate from lean body mass: BMR = 370 + 21.6 × lean body mass in kg. Lean body mass is your weight minus your fat mass. Because it uses lean mass directly, it does not need your age, height or sex.
Is Katch-McArdle more accurate than Mifflin-St Jeor?
It can be, if your body fat estimate is accurate. It suits people whose body composition is far from average, such as very lean or very muscular people. If your body fat number is a rough guess, Mifflin-St Jeor is usually the safer choice. The calculator shows both so you can compare.
What if I don't know my body fat percentage?
Use the main TDEE calculator with Mifflin-St Jeor, which doesn't need it. Guessing body fat adds error. An estimate that is 5 points off changes the result by roughly 85 calories for an 80 kg person.
Why doesn't Katch-McArdle ask for my sex?
Other equations use sex as a rough stand-in for how much muscle you carry. Katch-McArdle already has your lean mass, so it doesn't need that stand-in. Two people with the same weight and body fat get the same result.
How do I turn BMR into daily calories?
Multiply BMR by your activity factor, from 1.2 for sedentary to 1.9 for athletes. That gives your TDEE, the calories you need to maintain your weight. The calculator does this for you and adds targets for losing or gaining.

Related

TDEE calculatorDaily calories with three formulas. Bulking calculatorCalories and macros for building muscle. Which TDEE formula?When Katch-McArdle is the better fit.

Sources

  1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. PubMed 2305711
  2. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775–789. PubMed 15883556
  3. Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. PubMed 28642676