What makes Katch-McArdle different from other BMR formulas?

Most formulas (Harris-Benedict, Mifflin-St Jeor) use total body weight, age, and sex. Katch-McArdle uses only lean body mass, so it is more accurate for people with above-average muscle mass or very low body fat who would otherwise get an inflated estimate.

How do I find my body fat percentage?

The most accurate methods are DEXA scan, hydrostatic weighing, or an InBody device. Handheld impedance scales and skinfold calipers are less precise but widely available. Online estimation tools based on measurements are a reasonable starting point.

What is lean body mass?

Lean body mass (LBM) is everything in your body that is not fat — muscles, bones, organs, water, and connective tissue. LBM = total weight × (1 − body fat % / 100).

What activity multiplier should I use?

Sedentary (desk job, no exercise) = 1.2. Light activity (1–3 days/week) = 1.375. Moderate (3–5 days/week) = 1.55. Very active (6–7 days/week hard training) = 1.725. Extra active (physical job + hard daily training) = 1.9.

Is BMR the same as TDEE?

No. BMR is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) multiplies BMR by your activity factor to estimate actual daily burn including movement and exercise.

How many calories should I eat to lose weight?

A deficit of 500 calories per day below TDEE produces roughly 0.5 kg (1 lb) of fat loss per week. Deficits larger than 1,000 calories risk muscle loss; consult a dietitian for personalized guidance.

BMR Katch-McArdle Calculator

Name: BMR Katch-McArdle Calculator
Availability: InStock
Author: Nham Vu

Enter your weight, body fat percentage, and activity level to get your precise BMR and daily calorie needs using the Katch-McArdle lean mass formula.

Your Measurements

Body Weight (kg)

Body Fat Percentage (%)

If unsure, use a body fat estimation tool first.

Lean Body Mass — kg

Activity Level

Enter your details and click Calculate to see your results.

Summary

Enter your weight, body fat percentage, and activity level to get your precise BMR and daily calorie needs using the Katch-McArdle lean mass formula.

How it works

Enter your total body weight and body fat percentage.
The calculator derives your lean body mass (weight minus fat mass).
The Katch-McArdle formula applies: BMR = 370 + (21.6 × lean mass in kg).
Select your activity level to compute your Total Daily Energy Expenditure (TDEE).
Review your BMR, TDEE, and the calorie targets for weight loss or gain.

Use cases

Athletes and bodybuilders who track body composition want a formula that rewards muscle mass.
People who have had a DEXA scan or InBody test and know their exact body fat percentage.
Comparing BMR accuracy between Katch-McArdle, Mifflin-St Jeor, and Harris-Benedict.
Setting calorie targets for a cut, bulk, or body-recomposition phase.
Personal trainers building nutrition plans for clients with known body fat data.
Tracking how BMR changes as body composition improves over time.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu