Body Fat
18.70%
Fat Mass
14.96kg
Lean Mass
65.04kg
Rates & sources
Population-average body composition metrics. Always consult a qualified clinician before making health decisions.
Source: NHS — Health A-Z — figures refreshed at the start of each tax year.
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 US 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 optimistic assumptions without testing a more cautious scenario as well.
- !Comparing outputs from different tools without checking that the inputs match.
- !Treating the result as a final figure rather than a broad planning indicator.
- !Entering estimated rather than accurately measured height or weight, which can shift BMI or healthy-weight results meaningfully.
- !Interpreting a single metric in isolation instead of reading it alongside the other outputs the tool provides.
What to do next
- Rerun the calculator in six to eight weeks with updated measurements to track progress objectively.
- Use the related health calculators to build a fuller picture before discussing any changes with a professional.
- Open one of the linked guides if you want more context on what the metrics mean and how they relate to each other.
- If a result falls outside the normal range, book a GP appointment to discuss it rather than acting on the figure alone.
- Note the date alongside your results so you have a clear before-and-after record when you recheck later.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.
End-of-article next steps
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