Body Fat Calculator

Add body measurements?

The body fat calculator is a formula-based calculator that avoids the need for specialized equipment and technicians by estimating body fat percentage from a few simple measurements. The body fat calculator can be used with or without body measurements.

Although research shows a margin of variation between the results from formula and the results from other assessment methods such as bioelectrical impedance (BIA), research also shows that the variance is not large6

Recent research has also confirmed that the formula method is useful for categorizing against a standard 6 but isn't valid for quantitative research 6. In other words, a formula is good for assessing whether you fall into a lower or higher body fat percentage bracket, but you wouldn't use this method for research purposes.

Body fat can be expensive to measure and unreliable, but the body fat percentage calculator provides a quick - and surprisingly good - result.

Who Keeps Track of Body Fat?

Military personnel

For many US military personnel, keeping body fat within defined percentages is a requirement of the job and impacts retention and promotion opportunities.

Bodybuilders and elite athletes

Bodybuilders are amongst the most attentive when it comes to body fat percentages, constantly monitoring and tweaking.

Anyone interested in general health and fitness

For anyone interested in health and fitness, body fat percentage is no longer out of reach but is a relevant metric that anyone can use in their health and fitness journeys.

Limitations and Errors of Body Fat Calculators

Fat percentages derived from formulas all have different rates of error. Each formula's accuracy is equal to or worse than 95%. Formulas to calculate body fat are estimations and not 100% accurate.

Body fat percentage, lean body mass, water volume, dry lean mass are rough estimates and should be considered starting points in your endeavor to find your body composition.

Calculating body fat without measuring waist and other body areas assumes whole-body fat and cannot differentiate a large amount of muscle or location of fats.

Excess fat around your abdomen (visceral fat) is the most dangerous fat for your health. Boer, James, Hume, and others do not consider this into their equations.

When calculated with body measurements, a body fat percentage calculator, is an accurate tool to estimate body fat compared to BMI or hip to waist ratio. Body fat calculations with body measurements account for body fat collecting areas, the waist, neck, and hips. Body fat calculations are based on statistical analysis.

The addition of both waist and neck measurements for adult men and the waist, neck, and hip measurements for women dramatically increases the overall accuracy of the body fat percentage estimate.

Body Fat Formulas Are Not Suitable for Everyone

Bodybuilders, athletes, and pregnant women's results can vary and show incorrect body fat percentages. Body fat percentage can also vary depending on your age, sex, activity level, geological location, ethnicity, and diet.


  1. Institute of Medicine (US) Committee on Military Nutrition Research; Marriott BM, Grumstrup-Scott J, editors. Body Composition and Physical Performance: Applications For the Military Services. Washington (DC): National Academies Press (US); 1990. 4, Body Composition In The Military Services: Standards And Methods. Available from:
  2. Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol. 1984 Oct;247(4 Pt 2):F632-6. doi: 10.1152/ajprenal.1984.247.4.F632. PMID: 6496691.
  3. DHSS/MRC Group on Obesity Research. & Waterlow, J. C. & James, W. P. T. (1976). Research on obesity : a report of the DHSS/MRC group. London : H.M.S.O: ISBN 0114500347
  4. Hume R. Prediction of lean body mass from height and weight. J Clin Pathol. 1966 Jul;19(4):389-91. doi: 10.1136/jcp.19.4.389. PMID: 5929341; PMCID: PMC473290.
  5. Watson PE, Watson ID, Batt RD. Total body water volumes for adult males and females estimated from simple anthropometric measurements. Am J Clin Nutr. 1980 Jan;33(1):27-39. doi: 10.1093/ajcn/33.1.27. PMID: 6986753.