Enter your measurements
Confirm you’re an adult, enter height, weight and waist, then choose a research equation.
18+ · FREE RFM CALCULATORBody fat
Body fat
calculator.
A free height-and-waist estimate with a clear equation.
Find a workout plan that fits your life.
Your starting point is personal. Your next step can be simple.
Private by defaultNo account needed
Approximate estimates and subjective scores.
How reliable is this?RFM EXAMPLEILLUSTRATIVE MEASUREMENTS
Height 180 cm · Waist 90 cmAbout 24%
Selected equationMale
64 − 20 × 180 ÷ 90 = 24
An equation-based estimate, without a photo.
Your starting point
FREEUse your own measurements for a separate equation-based estimate.
Measure horizontally at the top edge of your hip bone, after a normal exhale. Do not use the narrowest waist. Measurement guide
Free assessment and AI goal illustration. The personalized program and optional premium continuation are paid.
Not medical advice, a medical opinion, or a diagnosis. Photos cannot establish health, strength, or exercise ability.
TURN YOUR STARTING POINT INTO A ROUTINEYour 90-day
Your 90-day
fitness plan.
A routine informed by your goals, assessment and available time. Illustrated guides, a calendar and private tracking—all in one place. Includes 30 days of premium when you activate it; the plan and basic logging stay yours afterward.
Illustrated workoutsCalendarPrivate tracking
Build my planUS$9.99 once
Explore an example workout planThree steps.
One starting point.
See your RFM estimate
Read your separately labeled measurement estimate and the effect of small changes in tape placement.
Track your own progress
Choose to save your check-in privately and repeat with consistent measurements.
Calculate body fat using height and waist.
This free body fat percentage calculator uses Relative Fat Mass (RFM), a published equation based on the ratio of your height to your waist circumference. No photo or calipers are needed. You can enter centimetres and kilograms or inches and pounds; weight does not change the RFM equation.
Measure consistently
Stand upright. Place a horizontal tape at the top edge of your right hip bone, snug without compressing your skin. Read after a normal exhale.
Choose an equation
The body fat calculator has male and female research equations. Choosing one selects a formula; it does not establish your health or a personal goal.
Read an estimate
The result is approximate. We also show how a one-centimetre waist change affects the equation, to help explain measurement sensitivity.
Male equation64 − 20 × height ÷ waist
Female equation76 − 20 × height ÷ waist
Use the same units for height and waist. The calculator converts your selected units before applying the equation. See the original RFM study, measurement protocol and validation limits.
Questions before you start
Is this a Navy body fat calculator?
This tool uses Relative Fat Mass, not the U.S. Navy method. RFM uses height and waist. The Navy method uses a different equation and additional measurements, so its results should be labeled and compared separately.
Does the calculator work for women and men?
It offers the two sex-specific equations published by the researchers. The original validation sample covered ages 20–69. Accuracy may differ for people outside the study’s ages, populations or body shapes. This website is for adults 18+.
Is a waist calculation more accurate than an AI photo?
They use different evidence. RFM applies an equation to measurements; AI interprets visible features in a photo. This product has not validated its photo estimate against a reference method. Keep the results separate and avoid interpreting small differences as meaningful change.
Can I track body fat changes with this calculator?
You can choose to save check-ins privately. Use the same equation, tape placement and measurement conditions each time. Learn about private body fat progress tracking.