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Katch-McArdle Calculator

Health

Calculate your BMR and TDEE with the Katch-McArdle formula, which uses lean body mass and body fat percentage for a more precise estimate instantly.

Reviewed by the thecalcu.com team · Last updated July 9, 2026

Weight
kg
30200
Body Fat Percentage
%
360
Activity Level

Total Daily Energy Expenditure

0
BMR (Katch-McArdle)
0
Lean Body Mass
0
Fat Mass
0

What is a Katch-McArdle?

The Katch-McArdle Calculator estimates your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using lean body mass instead of total body weight, a distinction that matters most for athletes, bodybuilders, and anyone with above- or below-average muscle mass. Developed by exercise physiologists Frank Katch and William McArdle, the formula calculates BMR as 370 plus 21.6 times your lean body mass in kilograms, isolating the metabolically active tissue that actually drives your resting calorie burn.

Because fat tissue burns relatively few calories at rest compared to muscle, two people with identical body weight but different body fat percentages can have meaningfully different metabolic rates, something weight-only formulas like the Harris-Benedict Calculator can't capture. This calculator requires your body fat percentage as an input; if you don't already know it, check the Body Fat Calculator or Lean Body Mass Calculator first.

Why Use a Katch-McArdle Calculator?

If you're notably leaner or more muscular than average, weight-based BMR formulas can meaningfully over- or underestimate your actual metabolic rate, throwing off your calorie targets for weight loss or muscle gain. The Katch-McArdle formula corrects for this by anchoring directly to lean body mass, giving athletes and lifters a more personalized starting point.

It's especially useful during a structured training cycle: as you build muscle or reduce body fat, your lean mass shifts, and recalculating here keeps your TDEE estimate, and therefore your calorie targets, aligned with your actual current physiology rather than a static weight-based guess.

Who Should Use This Calculator?

  • Bodybuilders and strength athletes with above-average muscle mass who find weight-only BMR formulas consistently overestimate or underestimate their needs.
  • Endurance athletes and very lean individuals whose low body fat percentage makes lean-mass-based calculations more representative of their true metabolism.
  • Anyone in a structured cutting or bulking phase who wants calorie targets that adjust as their body composition changes.
  • People who already know their body fat percentage from a DEXA scan, calipers, or a smart scale, and want to put that data to more precise use.
  • Fitness coaches building individualized calorie plans for clients with atypical body composition, best paired with the TDEE Calculator for cross-checking.

What Insights Does the Katch-McArdle Calculator Give You?

  • Total Daily Energy Expenditure, the primary result, your estimated total calorie burn per day including your selected activity level, ready to use as a calorie planning baseline.
  • BMR (Katch-McArdle), your resting-only energy need based on lean body mass, before any activity multiplier is applied.
  • Lean Body Mass, the metabolically active portion of your body weight, calculated from your total weight and body fat percentage.
  • Fat Mass, your estimated total fat weight in kilograms, the remainder after lean body mass is subtracted from total weight.

Compare your TDEE here against a weight-only estimate from the Harris-Benedict Calculator, a large gap between the two often signals that your body composition differs meaningfully from population averages.

How to use this Katch-McArdle calculator

  1. Enter your Weight in kilograms using the slider or number field.
  2. Enter your Body Fat Percentage, use the Body Fat Calculator first if you don't already have this figure.
  3. Choose your Activity Level from the five options shown, each with a description to help you select accurately.
  4. Review your Total Daily Energy Expenditure result, along with your BMR, lean body mass, and fat mass breakdown.
  5. Use the TDEE figure as your maintenance calorie baseline, adjusting up or down by roughly 500 kcal for a bulking or cutting goal.
  6. Recalculate periodically as your body fat percentage or weight changes to keep your targets accurate.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The Katch-McArdle formula first calculates lean body mass, then applies it to the BMR equation:

Fat Mass = Weight × Body Fat Percentage Lean Body Mass = Weight − Fat Mass BMR = 370 + (21.6 × Lean Body Mass in kg)

TDEE is then calculated by applying an activity multiplier:

TDEE = BMR × Activity Multiplier

| Activity Level | Multiplier |
|---|---|
| Sedentary | ×1.2 |
| Lightly Active | ×1.375 |
| Moderately Active | ×1.55 |
| Very Active | ×1.725 |
| Extra Active | ×1.9 |

Worked example: A person weighing 75 kg with 20% body fat has a fat mass of 15 kg and a lean body mass of 60 kg. Their BMR is 370 + (21.6 × 60) = 370 + 1,296 = 1,666 kcal/day. At a moderately active level (×1.55), their TDEE is approximately 2,582 kcal/day.

Frequently Asked Questions

What is the Katch-McArdle formula?
The Katch-McArdle formula estimates your Basal Metabolic Rate (BMR) using lean body mass rather than total body weight, calculated as BMR = 370 + (21.6 × lean body mass in kg). Because it isolates metabolically active tissue, it's often considered more accurate than weight-based formulas for people with unusually high or low muscle mass.
How is this different from the Harris-Benedict or BMR calculators?
The [Harris-Benedict Calculator](/harris-benedict-calculator/) and [BMR Calculator](/bmr-calculator/) estimate resting metabolism from total body weight, age, and height, without distinguishing muscle from fat. The Katch-McArdle formula instead uses your lean body mass directly, which is why it requires a body fat percentage input that those other formulas don't.
Why do I need to know my body fat percentage for this calculator?
Lean body mass, the input this formula actually depends on, is calculated by subtracting your fat mass from your total weight, and fat mass is derived from your body fat percentage. If you don't know your body fat percentage, use the [Body Fat Calculator](/body-fat-calculator/) first to get an estimate before returning here.
Who benefits most from using the Katch-McArdle formula?
Athletes, bodybuilders, and anyone who is notably leaner or more muscular than average tend to get more accurate results from Katch-McArdle than from weight-only formulas, since two people of the same weight can have very different lean mass. People with typical body composition usually see similar results from either method.
How accurate is my body fat percentage estimate?
Body fat percentage from at-home methods like skinfold calipers, tape measurements, or bioelectrical impedance scales typically has a margin of error of a few percentage points. Since Katch-McArdle is sensitive to this input, a more accurate body fat measurement (like DEXA or hydrostatic weighing, if available) will produce a more accurate BMR result.
What activity level should I select?
Choose Sedentary for a desk job with little exercise, Lightly Active for 1-3 days per week of exercise, Moderately Active for 3-5 days per week, Very Active for 6-7 days per week of hard training, and Extra Active for a combination of intense training and a physically demanding job. This multiplier is applied to your BMR to estimate your Total Daily Energy Expenditure (TDEE).
Can I use this calculator for a cutting or bulking phase?
Subtract roughly 500 calories from your TDEE for a typical cutting phase, or add roughly 500 calories for a lean bulk, then track your actual weight change over 2-3 weeks to fine-tune. Pairing this with the [Macro Calculator](/macro-calculator/) helps ensure the calories are allocated toward protein, carbs, and fat appropriately for your goal.
Does the Katch-McArdle formula work for very lean individuals?
Yes, this is actually one of its strengths, since very lean individuals (low body fat percentage) have proportionally more lean body mass relative to their weight, which weight-only formulas can underestimate. The formula scales directly with lean mass, making it well suited to athletic populations.
What is lean body mass exactly?
Lean body mass is your total body weight minus fat mass, encompassing muscle, bone, organs, water, and connective tissue. It's the metabolically active portion of your body that drives most of your resting calorie burn, which is why formulas based on it can be more precise for people with atypical body composition.
Should I recalculate as my body composition changes?
Yes, as you gain muscle or lose fat, your lean body mass changes, which directly shifts your Katch-McArdle BMR and TDEE. Recalculating every few weeks during an active training or diet phase, alongside an updated [Body Fat Calculator](/body-fat-calculator/) estimate, keeps your calorie targets aligned with your current body composition.
Also known as
Katch-McArdle formulaBMR by lean masslean body mass BMRKatch McArdle TDEEbody fat BMR calculator