Body Fat Calculator
Estimate body fat from a few tape measurements, and see fat mass and lean mass separately.
Body Fat Calculator
Body fat
19.21%
- CategoryAverage
- Fat mass14.98
- Lean mass63.02
- Your BMI25.47
Works out in your browser. Nothing you type is sent anywhere.
In short: Body Fat Calculator
From the measurements entered, body fat is around 19.21%, which falls in the Average band. That is 14.98 kilograms of fat and 63.02 of lean mass. BMI for the same height and weight reads 25.47, which is why the two tell you different things.
What is Body Fat?
Body fat percentage is the share of your weight that is fat rather than muscle, bone and water, estimated here from circumference measurements.
How is Body Fat calculated?
The US Navy method reads body fat from the difference between the waist and the neck, set against height, on a logarithmic scale. For women the hip measurement is added to the waist, and the constants differ. It is a population formula, so it estimates rather than measures.
- fatthe estimated body fat percentage
- waistthe waist circumference in centimetres
- neckthe neck circumference in centimetres
- heightheight in centimetres
A worked example
| Sex | Male |
|---|---|
| Age (years) | 30 |
| Height (cm) | 175 |
| Weight (kg) | 78 |
| Neck (cm) | 38 |
| Waist (cm) | 88 |
| Hip (cm, women only) | 95 |
| Result | |
| Body fat | 19.21% |
| Category | Average |
| Fat mass | 14.98 |
| Lean mass | 63.02 |
| Your BMI | 25.47 |
Every figure in this table is produced by the same calculation the tool above runs.
How to use this body fat calculator
- Enter sex, age, height and weight.
- Measure the neck below the larynx, and the waist at the navel.
- Women should also measure the hips at their widest point.
- Keep the tape snug but not tight, and read the estimate.
Questions people ask
How accurate is this method?
Within a few percentage points for most people, which is enough to track a direction over months. It is less accurate at the extremes, and it cannot match a scan. Measuring the same way each time matters more than the absolute figure.
How should I take the measurements?
Use a flexible tape, keep it level and snug without compressing the skin, and measure at the same time of day. The waist is taken at the navel and the neck just below the larynx. Measuring twice and taking the average removes most of the error.
Why does this differ from my smart scale?
A scale that reads body fat sends a small current through the body, and the answer moves with how hydrated you are, often by several points between morning and evening. Neither method is exact. Pick one and watch the trend rather than comparing the two.
What is a healthy body fat percentage?
It differs between men and women, because women carry more essential fat, and the bands shown here reflect that. A figure in the fit or average band is unremarkable. A doctor is the right person to tell you whether yours matters for your health.
Accuracy and sources
For general information. Not medical advice.
Checked by the Daytoolz team on 16 October 2026. How we check our tools.
Next, people use
- BMI CalculatorWork out your body mass index
- BMR CalculatorWork out the calories your body uses at complete rest
- Ideal Weight CalculatorSee the ideal weight for your height by three published formulas
- Calorie CalculatorWork out the calories a day that suit your goal
- Target Heart Rate CalculatorWork out your estimated maximum heart rate and the zones for light