katch mcardle calculator

What is the Katch-McArdle formula?

The Katch-McArdle formula estimates your Basal Metabolic Rate (BMR) using your lean body mass. Unlike many calorie equations that rely on age and sex, this one focuses on metabolically active tissue, which makes it very useful for people who know their body fat percentage.

The formula is:

BMR = 370 + (21.6 × Lean Body Mass in kg)

Then, to estimate total daily calorie needs, BMR is multiplied by an activity factor to produce TDEE (Total Daily Energy Expenditure).

Why people use a Katch mcardle calculator

• It is often more accurate for lifters and athletes with above-average muscle mass.
• It adjusts calorie estimates based on lean mass, not just total body weight.
• It gives a clear framework for maintenance, cutting, and bulking targets.

How this calculator works

Step 1: Estimate lean body mass

Your lean body mass is calculated from your body weight and body fat percentage:

Lean Body Mass = Weight × (1 - Body Fat % / 100)

Step 2: Calculate BMR

Using the Katch-McArdle equation, the calculator estimates the calories your body burns at rest in 24 hours.

Step 3: Apply activity level

BMR is multiplied by an activity factor (e.g., 1.2, 1.55, 1.9) to estimate your maintenance calories (TDEE).

Step 4: Add your goal adjustment

Choose a calorie adjustment for fat loss or muscle gain. Small adjustments are usually easier to sustain and track.

Tips for better accuracy

• Use a consistent method for body fat measurement (calipers, DEXA, smart scale trend, etc.).
• Track your body weight average over 2-3 weeks, not day to day.
• If progress stalls, adjust intake by about 100-200 kcal/day.
• Keep protein intake adequate during cuts and gains.

Katch-McArdle vs. other formulas

If your body fat estimate is reasonably accurate, Katch-McArdle is often superior to formulas that do not consider lean mass directly. If body fat is unknown, equations like Mifflin-St Jeor may be easier to use with available data.

Important note

Any calorie formula is an estimate. Real-world metabolism changes with sleep, stress, training quality, hormones, and adaptive responses over time. Use the output as a starting point, then refine based on actual weekly results.