TRANSPARENT BY DESIGN
Methods, with context.
A calculation is only useful when you know what it uses. Each tool preserves its method and source inputs.
Calculation reference
Body composition
Body fat, BMI, and measurement ratios.
Body fat calculator
Compare tape, BMI, and skinfold methods, or add a known body-fat result.
- Gallagher proposed body-fat ranges linked to BMI reference limits.
- ACE body-fat fitness categories.
- ACSM fitness assessment manual; adapted age-specific categories.
- CUN-BAE body-fat equation.
- Department of Defense circumference equations.
- Jackson–Pollock generalized skinfold equations for men.
- Jackson–Pollock–Ward generalized skinfold equations for women and their standard errors.
- Generalized skinfold body-composition equations.
- Durnin–Womersley body-density equations.
- Durnin–Womersley and Jackson–Pollock–Ward skinfold equations compared with air-displacement plethysmography in 43 women.
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.
- Department of Defense circumference equations.
- The Navy circumference formulas for men and women, as used in a 2019 comparison study.
- Gallagher proposed body-fat ranges linked to BMI reference limits.
- ACE body-fat fitness categories.
- ACSM fitness assessment manual; adapted age-specific categories.
- Navy Guide 4 (June 2026): Step 2 reads body fat from tables by weight and height minus waist; limits 26% men, 36% women.
- AFMAN 36-2905 (March 24, 2026): body fat by InBody scale, or if none by tape tables by height and neck, abdomen, waist and buttocks; limits below 26% men, 36% women.
- SPFMAN 36-2905: Space Force body fat by a lab-grade test such as DXA, or if none by the same tape sites and its scoring table; 26.0% men, 36.0% women.
- MARADMIN 066/26: Marine Corps body fat by multi-site tape test or bioelectrical impedance; up to 26% men and 36% women at 285 or more on the PFT and CFT.
- Army ABCP FAQ (effective July 7, 2026): the tape test and other body fat methods are rescinded.
- Army Directive 2026-13: waist-to-height is the sole ABCP standard; no tape test or other body fat method may challenge it.
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.
- Wishnofsky (1958) estimated the calories in gained or lost body weight.
- Thomas et al. (2013) found the 3,500 kcal rule overestimates weight loss in supervised studies.
- Hall et al. (2011) model body weight change over time and give a 100 kJ per day per kg rule of thumb.
- NIDDK Body Weight Planner, a dynamic model of weight change.
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.
- Review of resting energy by age, sex category, and BMI. Confidence intervals describe group means.
- Mifflin–St Jeor resting energy equation.
- Revised Harris–Benedict coefficients.
- Cunningham 1980 proposes 500 + 22 × lean body mass.
- Fat-free mass and resting metabolic rate.
- Lists Katch–McArdle as 370 + 21.6 × fat-free mass, separate from Cunningham 500 + 22.
- Uses the Katch–McArdle formula, 370 + 21.6 × lean body mass in kg.
- HERITAGE body-fat estimates and population differences.
- Systematic review: Mifflin–St Jeor predicted resting energy within 10% of measured in more adults than other common equations, with noteworthy individual errors.
- Systematic review of the conditions and test length for measuring resting metabolic rate by indirect calorimetry.
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.
- Tanaka and colleagues report an age-predicted maximum heart-rate equation.
- Gulati and colleagues report a women-specific equation.
- A comparison documents limitations of age-predicted maximum heart rate.
- Polar, a heart-rate monitor maker, names five zones from 50% to 100% of maximum heart rate: very light, light, moderate, hard and maximum.
- The American Heart Association puts moderate-intensity activity at about 50–70% and vigorous activity at about 70–85% of maximum heart rate.
- The CDC rates moderate activity at 5 or 6 and vigorous activity from 7 or 8 on a 0 to 10 effort scale, and gives the talk test: talk but not sing at moderate effort, only a few words without pausing for breath at vigorous effort.
- The ACSM position stand classifies intensity by percent of heart-rate reserve and percent of maximum heart rate with different cut points, and says one method cannot be assumed equivalent to another.
- In 165 recreational runners, the first lactate threshold sat at 80.7 ± 4.9% of measured maximum heart rate, with wide differences between people.
- A 2025 review describes how Zone 2 training is commonly defined: low-intensity exercise below the lactate threshold.
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.
- NIAAA drinking-pattern definitions and quantity thresholds.
- US standard drink contains 14 grams of ethanol.
- MedlinePlus calorie counts for common servings of beer, wine, spirits and mixed drinks.
- Food composition context; actual drink values vary.
- Study of alcohol and substrate oxidation.
- FAO energy conversion factors: 29 kJ (7 kcal) per gram of alcohol and 17 kJ (4 kcal) per gram of carbohydrate.
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.
Measurement converter
Convert weight, volume, length, temperature, energy, distance, fuel economy, and rectangle area.
Each result identifies its equation and assumptions. Source and calculation checks are documented per method. Independent clinical review has not been completed. Published equations are not proof of individual accuracy.