How accurate is a percent body fat calculator?

Accuracy depends on method and measurement consistency. Tape-based formulas can be useful for trend tracking but can differ from lab methods like DEXA. The best use is repeating the same method over time under similar conditions.

What measurements do I need for the US Navy body fat method?

Typically height, waist, and neck for men, and height, waist, neck, and hip for women. The formula is sensitive to measurement technique, so consistency matters.

Why does this tool ask for age in the BMI method?

BMI-to-body-fat formulas use age as an input. Without it, the estimate becomes much less meaningful. If you do not know your age or want a better approach, use the Navy tape method.

Why do different calculators give different results?

Different calculators use different methods (tape equations, BMI approximations, smart scales, calipers). Each has different error patterns. Consistency over time matters more than picking the "perfect" calculator.

Can this diagnose health status?

No. This is an educational estimate only. It does not diagnose conditions or determine health. If you have health concerns, consult a qualified professional.

Percent Body Fat Calculator (Free, Instant)

About This Calculator

Body fat percentage is useful for tracking progress, but most people do not have access to lab methods like DEXA. This free percent body fat calculator gives a practical estimate using simple measurement-based methods. Pick a method, enter a few measurements (metric or imperial), and get an instant estimated body fat %. This is educational only and not medical advice. Measurement error is common and different methods can produce different numbers, so this is best used to track trends over time rather than obsess over a single reading. If your goal is body composition, nutrition quality matters. BeyondCal helps you go beyond calories by tracking protein plus micronutrients and electrolytes so your diet supports training, recovery, and consistency.

Instant estimate of body fat percentage from simple inputs
Two methods: US Navy tape (primary) and BMI-based estimate (fallback)
Metric + imperial supported
Optional fat mass + fat-free mass when weight is provided
Use it for trends over time, not a single "perfect" reading

Safety note

Educational calculator only. It does not provide medical advice, diagnosis, or treatment. If you have symptoms, take medications, are pregnant, or have medical conditions, review results with a licensed clinician or registered dietitian before acting on them.

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How It Works

Choose a method (US Navy or BMI-based): US Navy uses tape measurements (waist, neck, and hip for women). The BMI-based method is rougher and requires age.
Enter measurements in metric or imperial: The calculator converts units internally so the formulas are applied consistently. Small measurement errors can shift the result.
We run a standard published equation: For Navy, we apply the inch-based US Navy equations. For BMI, we estimate body fat from BMI, age, and sex.
Interpretation is informational: The interpretation bands are descriptive ranges often used in fitness contexts. They are not medical advice or a diagnosis.

Frequently Asked Questions

Disclaimer: Educational estimate only. Not medical advice. Results depend on measurement accuracy and method.

Read full disclaimer

This tool provides an estimate of body fat percentage for educational purposes only. It uses measurement-based formulas and your inputs to produce an approximate result. It does not diagnose health conditions, provide medical advice, or replace assessment by qualified professionals. Measurement error and method differences can significantly affect results. For personalized guidance, consult a qualified clinician or dietitian.

Nutrition quality drives body composition results. This tool estimates body fat percentage, but changing it depends on what you do daily. BeyondCal helps you track protein plus micronutrients and electrolytes so your nutrition supports training and recovery.

Try it for free!