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BMI Score

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Est. Body Fat

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*This is a statistical estimate, not a direct measurement.

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About

Not everyone has a caliper or tape measure handy. This estimator bridges the gap between the rough Body Mass Index (BMI) and true body composition. By incorporating age and gender into the calculation, it corrects some of BMI's inherent flaws. Older adults typically carry more visceral fat than younger individuals at the same weight. This tool applies the Deurenberg correction to provide a more nuanced health snapshot. It is an estimate based on population averages and serves as a frictionless starting point for health awareness.

BMI calculator body fat estimate health check deurenberg formula obesity index

Formulas

First, BMI is calculated as weight divided by height squared.

BMI = WeightkgHeightm2

Then, the Deurenberg formula adjusts for biological factors.

BF% = 1.20 × BMI + 0.23 × Age 10.8 × Gender 5.4

Where Gender = 1 for males and 0 for females.

Reference Data

ClassificationBMI RangeEst. Body Fat (Men)Est. Body Fat (Women)
Underweight< 18.5< 8%< 21%
Normal Weight18.5 - 24.98-19%21-32%
Overweight25 - 29.920-25%33-39%
Obese Class I30 - 34.926-30%40-45%
Obese Class II 35> 30%> 45%

Frequently Asked Questions

No. Since it relies on BMI, it cannot distinguish between muscle mass and fat mass. A bodybuilder with high weight will register as obese.
As we age, muscle mass naturally decreases (sarcopenia) and density changes. The formula accounts for this by slightly increasing the estimated fat percentage for every year of age.
It is a scientifically validated regression equation derived in 1991 that correlates BMI with body fat percentage across large population groups.
This specific implementation is calibrated for adults (age 18+). Children require different growth charts and percentiles.