Example result based on the prefilled values.
Body Fat
18.70%
Fat Mass
14.96kg
Lean Mass
65.04kg
Continue your plan
Useful next calculations
When to use this calculator
- Before setting a new health goal or checking whether a plan is realistic.
- When you want to compare different assumptions without tracking them manually.
- When you need a quick baseline before discussing the result with a professional.
- When you are starting a new fitness or diet programme and want an objective starting-point measurement.
- When you want to recheck your numbers after several weeks of change to see whether the metrics are moving in the right direction.
A realistic New Zealand planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Weight (kg)
80 kg
Height (cm)
178 cm
Neck Circumference (cm)
38
Waist Circumference (cm)
84 cm
After entering these figures, review body fat, fat mass and lean mass together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Body Fat
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Fat Mass
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Lean Mass
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This calculator estimates body fat percentage using circumference-based measurements, most commonly the US Navy method, which uses measurements of the neck, waist, and hips (for women) alongside height to derive an estimate. The underlying formula was developed and validated by the US Navy as a practical field assessment tool. While it avoids the need for specialist equipment, it is less precise than clinical methods such as DEXA scanning. Circumference measurements are sensitive to measurement technique — small errors in tape placement can shift the result by several percentage points. Treat your result as a useful guide for monitoring trends over time rather than as a clinically precise figure. For accurate body composition assessment, consult a healthcare professional.
Common mistakes
- !Using an assumption that is not supported by a current local quote, bill, statement or official source.
- !Treating a generic estimate as a lender, provider, payroll or tax authority decision.
- !Mixing monthly and annual inputs without converting them consistently.
- !Forgetting location-specific taxes, fees, eligibility rules or payroll deductions where they apply.
- !Testing only one scenario instead of checking how a cautious assumption changes the result.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.
- Use the result to prepare better questions for a lender, provider, adviser or employer rather than treating it as a final answer.
Frequently asked
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