THE TOOLKIT
Find your starting point.
Free calculators. Choose the question you want to answer.
Looking for a child BMI percentile? Use the CDC growth curve for ages 2–19 →
32 calculators
Body composition
Body fat, BMI, and measurement ratios.
Body fat calculator
Compare tape, BMI, and skinfold methods, or add a known body-fat result.
BMI calculator
Calculate adult BMI and see the standard category ranges. A child and teen option uses CDC BMI-for-age data.
Waist-to-height ratio calculator
Compare waist with height and see the waist measurement at a 0.5 ratio.
A Body Shape Index calculator
Calculate ABSI and compare it with the original age- and sex-specific reference data.
Body roundness index (BRI) calculator
Calculate the adult body roundness index from standing height and waist circumference. See the formula and measurement limits.
FFMI calculator
Calculate fat-free mass index, height-adjusted FFMI, fat mass index, and lean mass.
Ideal body weight calculator
Compare four historical weight equations and the adult BMI reference range.
Muscle mass calculator
Estimate skeletal muscle using waist-based equations and compare body-composition components.
Navy body fat calculator
Estimate body fat percentage with a tape measure, using the U.S. Navy circumference equations.
Visceral fat area calculator
Estimate visceral fat area from age and tape measurements using the Samouda equations.
Waist-to-hip ratio calculator
Compare waist and hip measurements using the same units.
Energy
Calorie needs, deficits, and weight-change scenarios.
TDEE and energy requirement calculator
Compare 2023 adult energy estimates and the 2005 age-specific equations.
Calorie deficit and weight-loss planner
Compare intake scenarios and model time to a lower goal weight.
Body weight planner
Explore a dynamic weight-change scenario with a goal date and a transparent model.
Calories burned calculator
Estimate energy from walking, running, cycling, or inline skating with speed-specific activity values.
Calories to fat calculator
Convert calories to pounds or kilograms of body fat, or body fat to calories, with the 3,500 kcal per pound rule.
Maximum fat loss calculator
Explore a theoretical limit on daily energy supplied by body fat.
Reverse diet calculator
Build a weekly calorie ramp from current intake to a supplied maintenance estimate.
RMR and BMR calculator
Compare resting energy equations, with optional fat-free mass inputs.
Nutrition
Protein, macros, hydration, and eating schedules.
Protein calculator
Compare protein planning ranges by activity, age, goal, and body-composition basis.
Macro calculator
Convert calories into protein, carbohydrate, and fat with eleven editable example splits.
Hydration calculator
Explore a daily water estimate with exercise and climate adjustments.
Intermittent fasting schedule calculator
Compare eating windows and see how a schedule crosses midnight.
Fitness
Training loads, heart rate, aerobic capacity, and recomposition.
Body recomposition calculator
Compare energy, protein, and body-composition scenarios using stated assumptions.
Heart-rate zone calculator
Compare maximum heart-rate equations and calculate five intensity ranges.
One-rep max calculator
Compare seven estimates of one-repetition maximum and calculate percentage loads.
VO₂ max calculator
Compare six field estimates of aerobic capacity, with method-specific limits.
Lifestyle
Caffeine, alcohol, creatine, and everyday habits.
Alcohol calorie calculator
Add drinks to compare energy, ethanol, and standard-drink amounts.
Caffeine calculator
Add timed caffeine servings and compare their modelled remainder at bedtime.
Creatine calculator
Convert published loading and maintenance rates into grams for comparison.
Longevity habits assessment
Review 26 habits across seven areas. Save your progress and choose a practical focus.
Utilities
Unit conversion for measurements and food energy.