Quick start
- Open the Body Fat Calculator.
- Enter formula sex, height, neck, waist, and hip when the female equation is selected.
- Use the first example, "Female tape example: 165 cm, 68 kg, neck 34, waist 78, hips 98", if you want to see a filled-out calculation before entering your own values.
- Calculate, read the formula line, then copy the result only after the units and assumptions look right.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Estimate body fat percentage without a scale that measures body composition.
- Track tape-measure changes over time.
- Compare estimated fat mass and lean mass.
- Use alongside BMI for a broader screening picture.
What this calculator is for
The Body Fat Calculator uses a Navy-style circumference equation to estimate body fat percentage, fat mass, and lean mass. The value is most useful for consistent trend checks, not diagnosis or official testing.
Use it when you want to: Estimate body fat percentage without a scale that measures body composition. Track tape-measure changes over time.
What to enter
Good answers start with clean inputs. Before calculating, check the labels, units, and dates so the tool is solving the same problem you actually have.
- Enter formula sex, height, neck, waist, and hip when the female equation is selected.
- Add weight if you want estimated fat mass and lean mass. Weight does not change the percentage equation.
- Keep the tape level, snug, and not digging into the skin, then use the same sites when comparing changes over time.
Example walkthrough
Try the calculator example: Female tape example: 165 cm, 68 kg, neck 34, waist 78, hips 98. The example result is About 29.74% body fat.
- For the female example, 165 cm height, 68 kg weight, 34 cm neck, 78 cm waist, and 98 cm hips returns about 29.74% body fat.
- Because weight was entered, the same result shows about 20.22 kg estimated fat mass and 47.78 kg estimated lean mass.
- For the male example, 180 cm height, 84 kg weight, 40 cm neck, and 88 cm waist returns about 16.94% body fat.
Formula and steps
In plain language: The calculator uses the common Navy-style circumference method: male estimate = 86.01 x log10(waist - neck) - 70.041 x log10(height) + 36.76; female estimate = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387, with measurements converted to inches. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
Read the formula note when you need to understand where the number came from, especially before comparing results over time.
How to read the answer
This is an educational Navy-style tape estimate. It is not a DEXA scan, medical diagnosis, official military record, or complete body composition assessment.
- Read the body fat percentage as a tape-method estimate, then look at fat mass and lean mass for context if weight was entered.
- A small change can come from measurement placement, posture, breathing, tape angle, or tape tension, not only body composition.
- Use one method consistently when tracking a trend. Do not compare this number with a scale, caliper, or scan as if every method uses the same assumptions.
Common mistakes to avoid
Most bad results come from a small input mistake or from using a rough estimate for a decision it cannot safely answer.
- Do not switch waist sites between checks. The male equation is especially sensitive to waist minus neck.
- Do not pull the tape tighter on later measurements just to see a lower number.
- Do not use the estimate as a diagnosis, official record, sport weight-class decision, or medical body composition test.
What to try next
A related health tool can help check the same topic from another angle, but one number should not replace proper care.
- Use Army Body Fat Calculator if you want the current Army one-site tape estimate instead.
- Use Lean Body Mass Calculator for a formula-based lean-mass comparison.
- Use BMI Calculator if you want the simpler adult height-and-weight screening number beside this tape estimate.
Sources and safety notes
This guide uses public-health, clinical, or peer-reviewed references where the calculator needs a specific formula or interpretation boundary.
Source links are provided for transparency, but they do not turn the calculator into medical advice or a replacement for professional care.
Worked examples for Body Fat Calculator
About 29.74% body fat
About 16.94% body fat
About 31.41% body fat
FAQ in plain language
When should I use the Body Fat Calculator?
Use it for simple educational checks, trend tracking, or planning tasks like these: Estimate body fat percentage without a scale that measures body composition. Track tape-measure changes over time. It can help you understand a number, but it cannot explain your whole health situation.
What do the main Body Fat Calculator inputs mean?
Enter formula sex, height, optional weight, neck, waist, and hip when the female equation is selected. The male equation uses waist minus neck with height. The female equation uses waist plus hip minus neck with height. Keep the tape level, snug, and consistent from one check to the next.
What is the Body Fat Calculator doing with my inputs?
In plain language: The calculator uses the common Navy-style circumference method: male estimate = 86.01 x log10(waist - neck) - 70.041 x log10(height) + 36.76; female estimate = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387, with measurements converted to inches. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
How should I read the Body Fat Calculator result?
Read the percentage as a Navy-style tape-method estimate, then use fat mass and lean mass as context if you entered weight. Small changes can come from tape placement, posture, breathing, or tension, so this is better for consistent trend checks than one-time diagnosis.
What formula does this body fat calculator use?
It uses the common Navy-style circumference equations. Male estimates use waist minus neck with height. Female estimates use waist plus hip minus neck with height. The calculator converts centimeters to inches internally because the published equation constants are inch-based.
Where should I measure neck, waist, and hips?
Use the same tape sites every time. For the neck, measure below the larynx without including shoulder muscles. For the waist, keep the tape level and measure after a normal relaxed exhale. For hips, measure around the widest part. A different site can change the answer quickly.
Why is weight optional?
Weight is not part of the percentage equation, but it lets the calculator estimate fat mass and lean mass. For example, 29.74% at 68 kg is about 20.22 kg estimated fat mass and 47.78 kg estimated lean mass.
Related tools
- Army Body Fat Calculator Estimate Army one-site tape body fat from weight and abdomen circumference.
- Lean Body Mass Calculator Estimate Boer lean body mass from height, weight, and formula sex.
- BMI Calculator Estimate adult body mass index and healthy BMI weight range.
Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Health & Fitness Browse the full category for related tools that help with the same job.
- All free tools Search the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guides Find more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resources Start here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.