Free Fitness
Calculators
Ten evidence-based tools for body composition, nutrition, and performance.
Body Composition
3 toolsBody Fat % at Each Age
Drag two sliders to explore body fat percentages at every age — male and female, 20s through 60s. A photorealistic visual reference atlas, no guesswork.
Open tool →Body Fat Calculator
U.S. Navy tape-measure method. Enter neck, waist, and hip circumferences to get your body fat percentage and category.
Open →FFMI Calculator
Fat-Free Mass Index — how close your lean mass sits to the natural ceiling (~25). Weight, height, body fat in; physique tier out.
Open →Nutrition & Energy
3 toolsTDEE Calculator
Total daily energy expenditure — the calorie foundation of any diet. Mifflin-St Jeor formula with activity multiplier.
Open →Macro Calculator
Protein, carb, and fat targets calibrated to your TDEE and goal — cut, maintain, or bulk. Grams per day and per meal.
Open →Calorie Deficit Calculator
Daily calorie target, projected timeline, and milestone dates. Works for cuts and lean bulks alike.
Open →Performance & Output
3 tools1RM Calculator
One-rep max from six classical formulas, plus training percentages for every rep range. Untrained to Elite tier.
Open →Strength Standards
Eight compound lifts benchmarked Untrained → Elite. Get your percentile rank and the weight that unlocks the next tier.
Open →Calories Burned
Search 240+ activities. Enter weight and duration; get calories burned with food-equivalent comparisons.
Open →Documentation
1 toolFrequently
asked
questions
Common questions about the math, the methods, and what lies beyond the calculator.
Yes — every calculator is 100% free. No account, no email, no signup. Enter your measurements, get your result instantly. The GainFrame iOS app extends this with AI-powered photo analysis and ongoing tracking.
The U.S. Navy tape-measure method has been validated to within ±3–4% of DEXA for most people — one of the most reliable self-assessment tools available. GainFrame's AI photo analysis can provide a more precise estimate from a single image.
TDEE — Total Daily Energy Expenditure — is the total calories you burn per day, rest plus activity. It's the foundation of every diet: eat under it to lose fat, at it to maintain, above it to build muscle.
Set the goal to lean bulk — roughly 300 calories above TDEE. The calculator prioritizes protein (~0.8g per lb of bodyweight), caps fat at ~25% of calories, and fills the remainder with carbs. Pair with progressive resistance training.
Yes. GainFrame is an iOS app that analyzes your progress photos with AI and returns body fat %, FFMI, twelve muscle scores, and macro recommendations — from a single photo, in under a minute.
One photo.
A complete body
composition report.
GainFrame’s AI analyzes your progress photos and returns body fat %, FFMI, twelve muscle scores, and custom macros — in under 60 seconds.
~60 sec to result
±2–4% vs DEXA
Free to start
