Body Fat Calculator - LeanFuel

Stop guessing your protein needs. Calculate your real body fat % in 60 seconds and get a protein target based on lean mass — not total weight. Try free for 7 days.

Most protein calculators use your total body weight — so at 220 lbs, they tell you to eat 220g of protein a day. That's wrong, and you know it.

LeanFuel uses the U.S. Navy Method to calculate your actual body fat percentage from simple tape measurements. Then it gives you a protein target based on your lean body mass — the muscle you actually need to fuel.

HOW IT WORKS

1. Enter your measurements (neck, waist, height, weight)
2. Get your body fat %, lean mass, and fat mass instantly
3. Receive a personalized daily protein target
4. Log your protein and hit your goal every day

SMART PROTEIN TARGETS Your target adjusts based on your fitness goal and activity level:

• Build Muscle: higher protein to fuel muscle growth
• Lose Fat: extra protein to preserve lean mass in a deficit
• Maintain: moderate protein for steady body composition
• Recomp: optimized for simultaneous fat loss and muscle gain

TRACK YOUR BODY RECOMPOSITION

• Body fat % over time (watch it go down)
• Lean mass over time (watch it go up)
• Protein target history with each measurement
• Real body recomp data — not just the scale

DAILY PROTEIN LOGGING

• 100+ built-in foods with verified protein values
• Quick-log in one tap or add your own custom foods
• Track daily grams vs. your target
• Watch your protein ring fill up throughout the day

STAY MOTIVATED

• Earn XP for logging, hitting targets, and measuring
• Level up through 15 ranks from Beginner to Recomp Master
• Unlock 19 achievement badges for streaks and milestones
• Maintain daily log streaks and target streaks

BUILT FOR YOUR LIFESTYLE

• Beautiful dark mode design
• BMI calculator included
• Metric and imperial units
• 30 languages supported
• No account required — your nutrition data stays on your device

Try LeanFuel free for 7 days. Then continue with a weekly ($4.99/week) or yearly ($29.99/year) subscription to unlock unlimited measurements, full charts, and all features.

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SUPPORT: support@jakubl.com X: @jakublaszczyk