Body Fat Percentage Calculator: US Navy Tape Method
Our body fat percentage calculator turns three tape measurements into an estimate you can repeat at home. You get the number, the plus or minus 3 to 4 point error band against DEXA, and the published category bands for your
Five steps
How our body fat percentage calculator works
The maths is only as good as the tape work. Do these five things the same way every time and your readings will actually be comparable.
Pick your units
Metric, imperial and stone are equals here. Choose one and every result comes back in it, including fat mass and lean mass. Switching units mid tracking is the fastest way to confuse yourself.
Measure your neck
Put the tape just below the larynx, sloping very slightly down at the front. Snug, not tight, and don't flex or shrug. Read to the nearest half centimetre with your shoulders relaxed.
Measure your waist
Men measure at the navel. Women measure at the narrowest point of the torso. Stand upright, breathe out normally, and keep the tape level all the way round rather than dipping at the back.
Hip, for women
Measure the widest point across the buttocks with your feet together and the tape parallel to the floor. Men leave this field alone. If something is missing or out of range, the error names the field and the fix.
Read the band, not the digit
The result gives a percentage, fat mass and lean mass, the published category bands by sex and age, and what if rows showing how far a 1 cm slip at the waist or neck moves the answer.
03
How we work
A clear path from first conversation to finished work.
Body composition calculators
BMI, Asian BMI, body fat, skinfold, relative fat mass, lean body mass, FFMI, ideal and healthy weight range, frame size and recomposition tools, each printing the classification systems side by side with stated error bands.
Fat distribution calculators
Waist circumference, waist to height ratio, waist to hip ratio, body roundness index and a visceral fat tape proxy, mapped to published thresholds and clearly labelled as tape measures rather than scan volumes.
Calorie and nutrition calculators
BMR, TDEE, calorie deficit and surplus, macros, protein, water, fibre, weight-loss time, check-in, reverse diet and alcohol tools, with intake floors, weekly rate caps and no finish-date countdowns.
Fitness calculators
Calories burned, walking and running energy cost from published MET values, heart rate zones, VO2 max field tests and one rep max estimates, shown gross and net where that distinction matters.
Competitors print one integer. We print the published classification bands side by side, the honest error band next to the result, and what the number cannot tell you.
Next tool
Which calculator answers what this one can't
Each card names the gap it fills, so you open the next tool for a reason rather than out of habit.
BMI in 30 seconds
Weight against height, with the WHO and Asia-Pacific tables shown together. It cannot tell you how much of that weight is fat, which is why it belongs next to this page.
Waist to height ratio
Reuses the waist figure you just took and checks it against the under 0.5 rule. It reads fat distribution, not total body fat.
Daily calorie needs
Your TDEE by activity level with a stated plus or minus 12.5 per cent band. It tells you what you burn, not what your body is made of.
Safe daily deficit
A daily calorie target with the 1 per cent of bodyweight per week cap and the intake floors built into the maths. No finish date countdown anywhere.
Every calculator we publish
Body composition, fat distribution, calories and fitness tools, each printing the classification systems side by side with stated error bands.
05 — Common questions
Questions people ask about the tape method
Frequently Asked Questions
- How accurate is the Navy tape method against a DEXA scan?
- Expect the result to land within about 3 to 4 percentage points of a DEXA reading, in either direction. That means a printed 22 per cent could reasonably be 18 or 26. We show the band beside the number for that reason. Use the estimate to follow a direction over weeks, and treat any single reading as approximate rather than settled.
- Where exactly do I put the tape?
- Neck just below the larynx, sloping slightly down at the front. Waist at the navel for men and at the narrowest point of the torso for women. Hip at the widest point across the buttocks, feet together, for women only. Keep the tape level and snug against skin without compressing it, and breathe out normally before you read.
- How often should I re-measure?
- Every two to four weeks is plenty. Tape estimates carry more noise than a real change over seven days, so weekly measuring mostly shows you technique wobble and hydration. Measure at the same time of day, before eating, in the same posture, and write every figure down. Four readings across two months tell a far clearer story than twenty rushed ones.
- Why does a 1 cm tape error matter so much?
- Waist and neck enter the equations as logarithms, so small measurement changes carry straight through to the percentage. The result panel prints what if rows for a 1 cm slip at the waist and a 1 cm slip at the neck, so you can see the size of the shift with your own figures. That is the case for trends over single readings.
- Who should not use this calculator?
- Anyone under 18 should use the child tools with CDC percentiles instead, since adult cut-offs do not apply during growth. It is also a poor fit during pregnancy, with significant fluid retention, and for very lean or heavily muscled bodies where the circumference equations were not developed. It is general information, not medical advice, so speak to your GP about a health decision.
- Do you store my measurements?
- No. The calculator is stateless. There are no accounts, no saved profiles and no measurement history on our side. Your unit preference lives in the page address or your own browser, nothing more. If you want a record, keep it yourself in a notebook or a phone note, because a written log is what makes the trend readable later.
Take the tape once, then follow the trend
You have a body fat percentage and its error band. Pair it with a height based reading and your daily energy needs, and the picture stops depending on any one number.