BMI & Body Fat Percentage Calculator (Deurenberg)

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Category Health & Nutrition

Gender

Age

Height (cm)

Weight (kg)

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About

Directly measuring body fat requires expensive equipment like DEXA scans or hydrostatic weighing. For the general population, mathematical approximations offer a "good enough" metric for tracking progress. This tool uses the Deurenberg Formula, published in the British Journal of Nutrition, which correlates Body Mass Index (BMI) with body fat percentage while correcting for age and gender.

Unlike simple BMI, which ignores composition, this formula acknowledges that older individuals and women naturally carry more essential fat than younger men at the same weight. It provides a more realistic snapshot of metabolic health than BMI alone.

Formulas

The Deurenberg Formula (1991) is used for the calculation:

BF% = (1.20 × BMI) + (0.23 × Age) − (10.8 × Sex) − 5.4

Where Sex is a binary variable:

{

1 for Men0 for Women

Reference Data

Classification	Women (% Fat)	Men (% Fat)
Essential Fat	10 - 13%	2 - 5%
Athletes	14 - 20%	6 - 13%
Fitness	21 - 24%	14 - 17%
Average	25 - 31%	18 - 24%
Obese	32% +	25% +

Frequently Asked Questions

It generally has a standard error of estimate of about 4-5%. It tends to overestimate body fat in highly muscular athletes (who have high BMIs but low fat) and underestimate it in people with very low muscle mass (sarcopenia).

The formula adds 0.23% per year of age. This reflects the biological reality that as we age, we tend to lose lean muscle mass and accumulate more visceral fat, even if our weight stays the same.

Calipers are more accurate if used by a trained professional. However, for self-measurement, this formula eliminates user error involved in pinching skinfolds, making it more consistent for tracking trends.