Body Composition Calculators, Guides &amp; Benchmarks

BMI Calculator

BMI calculator: calculate body mass index quickly and interpret the result with a body-neutral range context.

Body Fat Percentage Calculator

Estimate body fat percentage with the U.S. Navy circumference method.

Ideal Weight Calculator

Compare multiple legacy ideal-weight formulas and view a practical range instead of one fixed number.

Lean Body Mass Calculator

Estimate lean body mass (fat-free mass) using Boer, James, and Hume formulas from height and weight.

Planning Calculator

Body Recomposition Planner

Plan a realistic body-recomp timeline with body-fat targets, training frequency, calorie pacing, and protein guidance.

FFMI Calculator

FFMI calculator: calculate your Fat-Free Mass Index to gauge muscularity relative to height and compare against natural training benchmarks.

Waist-to-Hip Ratio Calculator

Calculate your waist-to-hip ratio and assess body composition using WHO guidelines.

Guides & Content

Read the supporting guides, explainers, and benchmarks

This section groups the content cluster behind body composition, including topical articles plus tool-focused walkthroughs where they add useful context.

41 pages

Guides

How to Calculate Your Ideal Weight

How to calculate your ideal weight using BMI, the Devine formula, body fat percentage, and waist-to-height ratio, plus why a healthy range beats one number.

How to Do a Body Recomposition

How to body recomp: build muscle and lose fat at the same time. Macro targets, training structure, recovery rules, and the realistic timeline expectations.

How to Measure Body Fat at Home: 4 Methods Compared

How to measure body fat at Home: 4 Methods Compared: compare the Navy tape method, smart scales, calipers, and visual estimation for home body fat measurement.

How to Track Body Fat Accurately

How to track body fat reliably. Standardize tape and caliper measurements, time them right, and turn the data into real body composition progress.

Glossary Terms

What Is BMI? Simply Explained

Understand BMI (Body Mass Index): its definition, how it's calculated using height and weight, what your score means, and why it's a key health indicator.

What Is Body Fat Percentage? Definition & How It's Measured

Learn what body fat percentage means, how it's calculated, the methods used to measure it (DEXA, BIA, calipers), and why it beats weight or BMI for health.

What Is FFMI? Simply Explained

Learn what FFMI (Fat-Free Mass Index) is, how to calculate it, and why this metric is important for assessing muscularity relative to height and body fat.

Body Composition 18 ITEMS

What Is Lean Body Mass? Simply Explained

Understand Lean Body Mass: its definition, why it matters for health and fitness, how to calculate it, and its impact on metabolism and body composition goals.

Checklists

Body Recomposition Checklist

Plan body recomposition with this actionable checklist. Simultaneously build muscle and burn fat through precise nutrition, effective training.

Comparisons

Body Composition 6 CRITERIA

BMI vs Body Fat Percentage

BMI vs body fat percentage: BMI is a weight-to-height ratio, body fat percentage measures adipose tissue directly. Pros, cons, and when each metric is most useful.

Body Composition 6 CRITERIA

Cutting vs Bulking: When to Do Each

Unravel the 'cutting' vs 'bulking' debate to plan body composition changes. Learn when to strategically focus on fat loss or muscle gain for peak fitness.

Body Composition 7 CRITERIA

How Accurate Is the Navy Body Fat Calculator vs Calipers

How accurate is the Navy body fat calculator? It reads within 3-4% of DEXA versus 2-3% for trained calipers. Navy wins on repeatability for solo tracking.

Benchmarks & Statistics

Body Composition 15 STATS

Body Composition Statistics: Body Fat & Lean Mass Norms

Evidence-based body composition statistics: average body fat percentages, lean mass norms by sex and age, measurement accuracy, and natural FFMI ceilings.

Formulas

Body Composition 5 VARIABLES

BMI Formula

BMI = weight in kilograms divided by height in meters squared. Quick screening number, blind to body composition. Cutoffs are 18.5 / 25 / 30 (WHO).

Body Fat Percentage Formula (US Navy)

US Navy circumference-based body fat. Men: 86.010·log10(waist−neck) − 70.041·log10(height) + 36.76. Women: 163.205·log10(waist+hip−neck) − 97.684·log10(height) − 78.387.

Body Composition 4 VARIABLES

Body Recomposition Formula

Body recomposition formula: target_weight = LBM / (1 − target_BF%/100). weekly_fat_loss = (current_weight − target_weight) / weeks.

Fat Loss 3 VARIABLES

Calorie Deficit Formula

The calorie deficit formula: daily deficit = TDEE minus intake, with 1 lb fat about 3,500 cal and 1 kg about 7,700 cal, plus a worked weekly-loss example.

Body Composition 2 VARIABLES

FFMI Formula: Kouri-Adjusted Fat-Free Mass Index

FFMI formula: FFMI = LBM_kg / (height_m)² + 6.1·(1.8 − height_m). The +6.1·(1.8−h) normalizes to a 1.8 m reference. Natural ceiling ~25 male, ~22 female.

mobility 6 VARIABLES

Flexibility Score Formula

Flexibility score: Beighton hypermobility (0-9) + FMS Deep Squat (0-3). Beighton ≥5 suggests hypermobility; FMS ≤2 flags movement dysfunction.

Ideal Weight Formula (Devine 1974)

Ideal weight formula from the Devine 1974 equation: men 50 + 2.3 kg per inch over 60, women 45.5 + 2.3, plus Robinson, Miller and Hamwi variants.

Fat Loss 4 VARIABLES

Katch-McArdle Formula

Katch-McArdle BMR = 370 + 21.6·LBM_kg. Uses lean body mass instead of total mass — more accurate when reliable body-fat data is available.

Body Composition 5 VARIABLES

Lean Body Mass Formula (Boer)

Lean body mass formula (Boer 1984). Male: LBM = 0.407·mass_kg + 0.267·height_cm − 19.2. Female: LBM = 0.252·mass_kg + 0.473·height_cm − 48.3.

Max Muscular Potential Formula (Natural Ceiling)

Max muscular potential formula: natural FFMI ceiling near 25 for men and 21 for women (Kouri 1995), with monthly muscle gain rates by training age.

Nutrition Planning 3 VARIABLES

Protein Intake Formula

protein_g = mass_kg × goal_factor. Goal factors: 0.8 sedentary (RDA), 1.6 trained baseline, 1.8 deficit / hypertrophy, 2.2 advanced cut or older lifter.

Waist-to-Hip Ratio Formula

Computes waist-to-hip ratio as waist circumference divided by hip circumference; WHO cardiometabolic risk cutoffs are 0.90 for men and 0.85 for women.

Examples

BMI Examples

Explore practical BMI examples across diverse scenarios, from athletes to seniors, revealing key insights into its utility and limitations for health.

Body Fat Examples

Explore diverse real-world body fat examples, from sedentary professionals to athletes and new mothers, revealing unique insights into health, performance.

Body Recomposition Examples

Explore real-world body recomposition examples, from busy professionals to athletes and new parents, revealing how to build muscle and lose fat.

FFMI Examples

Explore practical FFMI examples for athletes, beginners, and older adults. Learn how Fat-Free Mass Index reveals body composition and natural muscle limits.

Ideal Weight Examples

Discover diverse ideal weight examples for athletes, sedentary individuals, and more. Learn how factors like body composition, age, and lifestyle redefine.