PeakCalcs

Body Composition Calculators

Estimate body fat percentage, BMI, ideal weight, and more using validated measurement methods with multi-formula comparison.

Latest in Body Composition

Body Fat Calculator

Estimate body fat from Navy tape, Jackson-Pollock 3- and 7-site skinfold, and Deurenberg BMI-derived methods. Compare four validated formulas side by side.

BMI Calculator

Calculate your BMI in kg/m² with WHO bands (18.5–24.9 healthy, 25+ overweight), BMI Prime ratio, and your personalised healthy-weight target range.

Ideal Weight Calculator

Estimate ideal body weight from Hamwi, Devine, Robinson, and Miller formulas with the WHO BMI 18.5–24.9 healthy range. Free side-by-side comparison.

Waist-to-Hip Ratio Calculator — WHO Risk

Calculate your waist-to-hip ratio against WHO sex-specific risk cut-points (0.85 female, 0.90 male) from two simple tape measurements.

Body Surface Area Calculator — Du Bois & Mosteller

Calculate body surface area in m² from Du Bois and Mosteller formulas side by side. Free BSA tool for clinical reference and training-load normalising.

Military Body Fat Calculator — DoD Tape Test

Estimate body fat from neck and waist tape sites with the Hodgdon-Friedl DoD equation and pass-or-fail against US Army, Navy, and USAF limits.

BMI Category Checker

Check your BMI against WHO bands (18.5–24.9 healthy, 25+ overweight), with BMI Prime ratio and a Deurenberg body fat estimate. Free analysis tool.

Pregnancy Weight Gain Calculator — IOM Guidelines

Estimate pregnancy weight-gain range by trimester from IOM 2009 guidelines, BMI-adjusted across underweight, normal, overweight, and twin pregnancy.

FFMI Calculator

Calculate your Fat-Free Mass Index with normalised FFMI adjusted to 1.8m height. Includes natural muscular potential ceiling and category interpretation.

Waist-to-Height Ratio Calculator — 0.5 Threshold

Calculate your waist-to-height ratio with the universal 0.5 boundary threshold. Compare WHtR risk categories backed by Ashwell meta-analysis research.

Lean Body Mass Calculator — Direct & Estimated

Calculate lean body mass from body fat percentage or estimate it with the Boer 1984 formula. Includes fat mass breakdown and LBM as percentage of total.

Ponderal Index Calculator — Height-Cubed Metric

Calculate your Ponderal Index in kg/m³ from height cubed for a body-build metric that handles tall and short builds more honestly than BMI alone.

Body Roundness Index Calculator — Thomas 2013

Calculate your Body Roundness Index from waist circumference and height using the Thomas 2013 eccentricity formula. Includes estimated body fat range.

How to Measure Body Fat — Complete Method Guide

Compare body-fat methods: Navy tape, Jackson-Pollock skinfold, BIA scales, DEXA, and hydrostatic weighing. Accuracy, cost, and technique for each method.

Healthy Body Fat Percentage by Age — Ranges

Evidence-based body-fat ranges by age bracket and sex. ACE category bands, 3% male and 12% female essential-fat floors, and why "lower" is not healthier.

BMI Alternatives

BMI told you a number. Eight better body-composition metrics — BF%, FFMI, WHtR, WHR, BRI, BSA, Ponderal Index — with equipment-need-and-when-to-use guide.

Body Fat Percentage for Women in Their 40s

Healthy body fat ranges for women in their 40s by ACE category, and how perimenopause shifts fat toward the midsection — what changes and what doesn't.

Body Fat Percentage for Women in Their 50s

Healthy body fat ranges for women in their 50s by ACE category, and why the post-menopausal decade favours protecting bone and muscle over a low number.

Body Fat Percentage for Women in Their 60s

Healthy body fat ranges for women in their 60s by ACE category, and why functional capacity and muscle for independence matter more than a low number.

Body Fat Percentage for Women Over 70

Healthy body fat ranges for women over 70 by ACE category, and why slightly higher fat can be normal while unintentional weight loss is the bigger risk.

Body Fat Percentage for Women in Their 20s

Healthy body fat ranges for women in their 20s by ACE category, why this is the decade to build bone and muscle, and why chasing a low number costs most.

Body Fat Percentage for Women in Their 30s

Healthy body fat ranges for women in their 30s by ACE category, why pregnancy makes the number a moving target, and why your metabolism hasn't crashed.

Body Fat Percentage for Men in Their 20s

Healthy body fat ranges for men in their 20s by ACE category, the peak decade to build muscle and bone, and why the essential-fat floor is a hard minimum.

Body Fat Percentage for Men in Their 40s

Healthy body fat ranges for men in their 40s by ACE category, and why the scale can stay flat while muscle slips and visceral fat climbs.

Body Fat Percentage for Men in Their 50s

Healthy body fat ranges for men in their 50s by ACE category, and why visceral-fat risk and accelerating muscle loss matter more than the number.

Body Fat Percentage for Men Over 60

Healthy body fat ranges for men over 60 by ACE category, and why preserving muscle and reserve matters far more than chasing a lower number.

Athletic vs Average Body Fat Explained

Athletic vs average body fat: how the standards differ, what athletes across sports carry on DXA, and why athletic-low fat is not a health target.