Body Fat Percentage Calculator

Estimate only, not medical advice. This is the U.S. Navy circumference method applied to the tape measurements you type. It does not diagnose obesity or any other condition, and it is not a substitute for a clinical evaluation or for a lab method such as DEXA. Category labels are the bands this page uses. They are not a medical classification of you.

How the percentage is calculated

All inputs are inches. Height is standing height. Neck, waist, and, for the female formula, hip are circumferences. The page uses base-10 logarithms. For the male formula: body fat percent = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For the female formula: body fat percent = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. The result is rounded to one decimal place for display.

The sex field selects the formula. It is not a full medical history. The hip field appears only for the female formula, and the page will not calculate a female result without it. If waist is not larger than neck in the male formula, or if waist plus hip is not larger than neck in the female formula, the logarithm's input is not positive and the result is not a meaningful percent. Recheck the tape. The page also warns when the result is under 2 percent or over 60 percent, which is outside the range it treats as typical, and it still shows the number so you can see the inputs were accepted.

The category label uses fixed cutoffs on that percent. For the male formula: under 6 is labeled essential fat, from 6 up to but not including 14 is athletes, from 14 up to but not including 18 is fitness, from 18 up to but not including 25 is average, and 25 or above is obese. For the female formula: under 14 essential fat, from 14 up to but not including 21 athletes, from 21 up to but not including 25 fitness, from 25 up to but not including 32 average, and 32 or above obese. These bands follow a widely used American Council on Exercise style of grouping. Other charts draw the lines in different places. The label you see is this page's label, produced by those cutoffs only.

Worked examples

Example 1: Male formula

Height 70 inches, neck 15 inches, waist 34 inches. The circumference term is 34 − 15 = 19. Body fat percent = 86.010 × log10(19) − 70.041 × log10(70) + 36.76, which is 17.5 percent on this page. 17.5 falls in the fitness band (14 up to 18). A tighter tape technique that reads the waist an inch smaller changes the log term and can move the result by more than a trivial amount. Measure twice and average, and write the method down so the next reading uses the same sites.

Example 2: Female formula

Height 64 inches, neck 13, waist 28, hip 38. The circumference term is 28 + 38 − 13 = 53. Body fat percent = 163.205 × log10(53) − 97.684 × log10(64) − 78.387, which is 26.6 percent here. That falls in the average band (25 up to 32). Leaving the hip blank blocks the calculation. Using the male formula on the same waist and neck would answer a different equation. Pick the formula that matches the measurement set you took.

Example 3: A result the page flags

If the tapes produce a number under 2 or over 60, the warning appears and the percent still prints. That is a prompt to remeasure, not a diagnosis at either extreme. Swapped fields are a common cause: a height typed into the waist box, or a waist in centimeters typed into an inches field. Convert centimeters to inches first with the Length Converter.

Example 4: Tracking a change, not a single reading

Suppose a later male measurement, taken the same way, comes out 2 percentage points lower. The Percent Change Calculator can describe that move relative to the first reading. A two-point move that comes from a different tape position is not a change in body composition. Consistency of site, tape tension, and time of day is what makes a series readable. A single Navy estimate next to a single BMI is a snapshot. The BMI versus body composition note on this site walks through why those two snapshots answer different questions.

When to use this

Use it when you want a tape-measure estimate and you can take the circumferences the formula expects. It is a practical option when you will not be going to a lab, and it is a reasonable way to watch direction over months if you repeat the method. It is a poor substitute for a DEXA or hydrostatic measurement when a clinician, a coach, or a qualifying standard needs a lab number. The Navy developed the equations to estimate body fat from body circles for service screening. This page runs those equations. It does not apply current military standards, age adjustments, or any waiver process.

BMI from height and weight is the companion number, not a duplicate. A muscular person can have a BMI in a high band and a tape estimate in a lower band, or the reverse can happen. Run the BMI Calculator if you want that second view. Neither one is a health exam. The background on where the Navy equation came from and how the sites are defined is in The Navy Body Fat Formula Explained.

How to take the measurements

Use a soft tape, not a steel carpenter's tape, and stand relaxed. Do not pull the stomach in and do not push it out. Take each site twice and average the two readings if they differ. Height is without shoes.

Neck: just below the larynx, with the tape sloping slightly downward toward the front, snug and not tight enough to crease the skin. Waist for the male formula: at the navel, level around the body. Waist for the female formula: at the narrowest point of the waist. Hip, female formula only: at the widest point of the hips and buttocks. These sites are the ones the published method uses. Measuring the waist at a different landmark, such as the iliac crest when the formula expected the navel, feeds the equation a number it was not built on. The page cannot tell which landmark you used. It only sees inches.

Common mistakes

• Centimeters in an inches field. A 90-centimeter waist typed as 90 inches blows up the log term. Convert first.
• Using the male formula because the hip field is hidden. The hip field hides until you select the female formula. Select the formula, then measure hip.
• Pulling the tape tight or sucking in. Both shrink the circumference and lower the estimate. Repeat the way you will repeat it next month.
• Reading the category as a clinical diagnosis. "Obese" on this page means the percent crossed the cutoff coded here. It is not a doctor's assessment.
• Comparing today's tape with last month's different site. A navel measurement and a "where my jeans sit" measurement are different inputs.
• Expecting the result to match a smart scale or a DEXA printout. Those are other methods. Agreement within a small band is possible and not guaranteed. This page does not claim an error bar.
• Averaging a male-formula result and a female-formula result. They are different equations. Use one.

Limitations

Two equations, inches only, one decimal on output, and category cutoffs as listed above. No age term, no ethnicity term, no adjustment for pregnancy, and no check that the person measured matches the formula selected beyond the fields on the form. The method estimates. It does not measure fat mass directly. Hydration, recent exercise, and tape tension move circumferences. A warning fires under 2 percent and over 60 percent. Values inside that window can still be a poor estimate for a given person. Military tables and ACE charts are separate documents. If you need the table your organization uses this year, read that table. Do not assume these labels are it.

FAQ

Why do the male and female formulas differ?

They were built as separate equations, and the female equation includes hip circumference. Essential fat ranges also differ, which is why the category cutoffs on this page start higher for the female formula. Pick the equation that matches the measurements you took.

How close is this to a DEXA scan?

Close enough to be useful for a personal trend, and not close enough to treat as a lab result. This page does not state a plus-or-minus accuracy figure, because that depends on measurement technique and on the reference method. If a decision depends on the true percent, get a direct measurement.

What does the warning "outside typical range" mean?

The computed percent is under 2 or over 60. Recheck units and landmarks. The number is still displayed so you can see what the formula returned.

Related calculators

• BMI Calculator
• TDEE Calculator. Body-fat percent is not an input on that page.
• Target Heart Rate Zones Calculator
• Daily Water Intake Calculator
• Length Converter for centimeters to inches
• The Navy Body Fat Formula Explained
• BMI vs body composition