Skip to content
Hustle Frolic

Body Fat Calculator

Estimate your body fat percentage using three validated methods — US Navy, RFM, and BMI-based. Compare results, understand your composition, and find your ideal range.

Units:
Your Stats
Measurement Method

How to measure accurately

1Measure your neck at the narrowest point just below the larynx. Keep the tape horizontal.
2Measure your waist at the navel (belly button) level. Exhale normally — don't suck in.
3Measure your hips at the widest point. Keep the tape parallel to the floor.
3Take each measurement twice and use the average for accuracy.

Relative Fat Mass — one measurement needed

1Measure your waist at the navel level. Exhale gently — don't brace or suck in.
2RFM only needs height and waist — simpler and more reproducible than multi-site methods.
3Validated in a 2018 PLOS ONE study as a stronger predictor of body fat % than BMI across diverse populations.

BMI-Based Estimation — no tape required

1Uses height, weight, age, and sex via the Deurenberg formula (1991) to estimate body fat.
2The least precise method — especially for muscular individuals — but useful when no tape measure is available.
3No additional inputs needed — uses the height and weight you already entered above.

Note: BMI-based BF% estimation carries ±5–8% error vs DEXA. Use the Navy or RFM method for better accuracy.

Your results will appear here

Fill in the form and press “Calculate My Body Fat %”.

Three ways to estimate body fat

  • US Navy method: uses your height, neck and waist (plus hips for women). With careful measuring it is usually within 3–4% of lab tests.
  • RFM (Relative Fat Mass): a 2018 formula that only needs your height and waist. It is simple and more accurate than BMI.
  • BMI-based estimate: needs no tape measure, but it is the least accurate, because it can't tell muscle from fat.

The calculator shows all three side by side, so you can see how close they are to each other.

How to measure accurately

Measure in the morning before eating, with a soft tape that sits flat on your skin without pressing in. Measure your waist at the navel, your neck just below the larynx, and (for women) your hips at the widest point. Measure twice and use the average.

What is a healthy body fat percentage?

For men, around 14–24% is a typical healthy range and 6–13% is athletic. For women, it is around 21–31% healthy and 14–20% athletic. Women naturally carry more essential fat, so the ranges are higher.

Track the trend, not one number

Every method has some error, so the real value is in re-measuring every 4–6 weeks with the same method. If your body fat is falling while your weight holds steady, you are building muscle. See where that muscle stands with the Lean Body Mass Calculator.

Fitness Calculators

More free tools

All calculators
Macro Calculator Get your personalised protein, carbohydrate, and fat targets — built around your goal, diet style, and training schedule. With a full meal plan and food pairing guide included. Calculate Now Fat Intake Calculator Calculate your ideal daily fat intake — broken down by type: saturated, monounsaturated, and polyunsaturated. With food sources, meal distribution, and what to avoid. Calculate Now Lean Body Mass Calculator Calculate your Lean Body Mass across four validated formulas — with a full body composition breakdown, ideal LBM range, training targets, and a roadmap to your goal physique. Calculate Now One Rep Max Calculator Calculate your estimated 1RM across seven validated formulas, get your complete training zone breakdown, rep-weight table, and a 4-week progressive overload plan. Calculate Now

Book A

Free Discovery Call

Not sure if coaching is right for you right now? Book a free 20-minute call. We'll talk about your goals, your current situation, and whether Hustle Frolic is the right fit - honestly.

Schedule a Call →