Free Katch-McArdle Calculator

Calculate your Basal Metabolic Rate (BMR) using the Katch-McArdle formula — the most accurate equation for people who know their body fat percentage. Unlike other BMR formulas, Katch-McArdle uses your lean body mass instead of total weight, making it ideal for athletes and fitness enthusiasts.

What is the Katch-McArdle Formula?

The Katch-McArdle formula is a method for estimating your Basal Metabolic Rate (BMR) based on your lean body mass (LBM). Unlike the Mifflin-St Jeor or Harris-Benedict equations, the Katch-McArdle equation does not require your age, gender, or height. It only needs two inputs: your total body weight and your body fat percentage.

This makes the Katch-McArdle formula particularly valuable for athletes, bodybuilders, and anyone with above-average muscle mass, because it accounts for the metabolic difference between lean tissue and fat tissue. Muscle burns significantly more calories at rest than fat, so using lean body mass produces a more accurate BMR estimate for fit individuals.

Lean Body Mass (LBM) is calculated as:
LBM = Weight × (1 - Body Fat % / 100)

For example, if you weigh 80 kg with 15% body fat, your lean body mass is 80 × (1 - 0.15) = 68 kg. Plugging that into the Katch-McArdle equation: BMR = 370 + (21.6 × 68) = 1,839 calories per day.

Katch-McArdle vs Mifflin-St Jeor: When to Use Each

Both the Katch-McArdle formula and the Mifflin-St Jeor equation are scientifically validated methods for estimating BMR, but they work best in different situations.

Use the Katch-McArdle calculator when:

• You know your body fat percentage (from DEXA, calipers, or another reliable method)
• You are an athlete, bodybuilder, or have above-average muscle mass
• You are very lean (below 12% body fat for men or 20% for women)
• You want the most accurate BMR estimate based on your actual body composition

Use Mifflin-St Jeor when:

• You do not know your body fat percentage
• You have an average body composition
• You want a reliable general-purpose BMR estimate

For most people with average body composition, both formulas will produce similar results. However, the Katch-McArdle equation becomes significantly more accurate for muscular individuals because a standard weight-based formula would overestimate their body fat and underestimate their BMR.

How to Estimate Your Body Fat Percentage

To use the Katch-McArdle calculator, you need to know your body fat percentage. Here are the most common methods to estimate it:

• Navy Body Fat Method: Uses measurements of your neck, waist, and hips (for women) to estimate body fat. This is the method used by our Body Fat Calculator.
• Skinfold Calipers: A trained professional measures skin folds at specific body sites to estimate subcutaneous fat. Accurate when performed correctly.
• DEXA Scan: Dual-energy X-ray absorptiometry is considered the gold standard for body composition analysis. It provides precise measurements of fat, muscle, and bone density.
• Visual Estimates: Comparing your physique to reference photos can give a rough estimate. Men at 10-15% and women at 18-25% are generally considered athletic.
• Bioelectrical Impedance (BIA): Many smart scales use electrical signals to estimate body fat. Accuracy varies by device and hydration level.

For the most accurate results with the Katch-McArdle formula, use a DEXA scan or professional skinfold caliper measurement. If those are not available, try our free Body Fat Calculator for a quick Navy method estimate.

Related Tools

Explore our other free nutrition calculators to complement your Katch-McArdle results:

• Body Fat Calculator - Estimate your body fat percentage using the Navy method
• TDEE Calculator - Compare 3 formulas including Katch-McArdle, Mifflin-St Jeor, and Harris-Benedict
• Mifflin-St Jeor Calculator - Calculate BMR without needing body fat percentage
• Macro Calculator - Calculate your optimal protein, carbs, and fat intake

For Nutrition Professionals

Are you a dietitian, nutritionist, or personal trainer looking to streamline client BMR calculations and meal planning? Foodzilla automatically calculates BMR using the Katch-McArdle formula and other validated equations, then generates personalized meal plans in seconds.

• Built-in Katch-McArdle, Mifflin-St Jeor, and Harris-Benedict calculators
• Automatic macro calculations based on client goals
• AI-powered meal plan generation
• 1,500+ dietitian-approved recipes
• White-label mobile apps for your clients