BMR Calculator — Katch-McArdle
Calculate your BMR using lean body mass — the most accurate formula when your body fat percentage is known.
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▸ Compare with Mifflin-St Jeor (optional)
When to use Katch-McArdle
This formula is the most accurate BMR calculator when you know your body fat percentage. Unlike Mifflin-St Jeor and Harris-Benedict, it uses lean body mass directly — meaning two people with the same weight but different body compositions will get different results.
Katch-McArdle vs other formulas
- Best for: athletes, bodybuilders, anyone who knows their BF%
- Mifflin-St Jeor: better when BF% is unknown
- Harris-Benedict: older, slightly less accurate
How the BMR Calculator — Katch-McArdle Works
The BMR Calculator — Katch-McArdle calculates your personalised intake target by combining your body weight, activity multiplier, and goal (weight loss, maintenance, or muscle gain). The underlying formulas are drawn from dietary reference intakes established by organisations including the WHO, NIH, and USDA.
Your result represents a daily target — a starting point calibrated to your inputs. Since individual metabolism varies, treat this as a well-researched baseline and adjust slightly based on real-world results over 2–4 weeks.
Frequently Asked Questions
How is my result calculated?
This calculator uses established nutrition science formulas and dietary reference intakes (DRIs) from organisations like the WHO, NIH, and USDA. Your inputs — body weight, activity level, and goal — are run through these equations to give a personalized recommendation.
Should I hit these numbers exactly every day?
Think of the output as a weekly average target, not a rigid daily rule. Natural day-to-day variation is normal and healthy. Consistently trending close to your targets over a week matters far more than hitting exact numbers each day.
How does activity level affect my results?
Activity level is one of the biggest factors in your nutritional needs. More active individuals need significantly more calories, protein, and carbohydrates to support energy demands and muscle repair. Updating your activity level when it changes keeps your targets accurate.
Do I need to track macros and calories?
Tracking both provides the most complete picture, but you don't have to do both at once. Many people find it easier to start with protein targets, then layer in calorie awareness once that habit is established. Use what level of detail works for your lifestyle.
How often should I recalculate my targets?
Recalculate every 4–8 weeks, or whenever your body weight changes by more than 5 lbs / 2 kg, you significantly change your activity level, or your goal shifts. Nutritional needs change as your body adapts.