Body Fat Percentage Calculator

Use our free body fat percentage calculator to estimate your body fat from simple tape measurements. Based on the US Navy method, it gives you your body fat %, fat mass, lean mass, and category in seconds.

Calculate Your Body Fat

Gender

Enter height and tape measurements in the units selected above. Weight is always in kilograms.

What Is Body Fat Percentage?

Body fat percentage is the share of your total body weight that is fat. If you weigh 75 kg and your body fat percentage is 19.3%, about 14.5 kg of your weight is fat and the remaining 60.5 kg is lean mass, which includes muscle, bone, water, and organs.

Two people can share the same scale weight and look completely different, because muscle is denser than fat. That is why body fat percentage is a better measure of body composition than weight alone, and why it is more useful than BMI for people who lift weights or play sports. Tracking it over time shows whether a diet or training plan is burning fat, building muscle, or both. A body fat percentage calculator separates the two, so you can see whether a change on the scale is fat or muscle.

How This Body Fat Percentage Calculator Works

This body fat percentage calculator uses the US Navy method, developed by Hodgdon and Beckett in 1984 for the United States Navy. It estimates body fat from your height and a few tape measurements: neck and waist for men, plus hips for women. The Navy needed a fast field test that did not require calipers or a lab, and this formula is still one of the most practical options today.

Enter your measurements, choose your units, and press Calculate. The calculator converts centimeters to inches where needed, then applies the Navy formula. That is all it takes for this body fat percentage calculator to return your result.

For men: Body fat % = 86.010 x log10(waist – neck) – 70.041 x log10(height) + 36.76

For women: Body fat % = 163.205 x log10(waist + hips – neck) – 97.684 x log10(height) – 78.387

All tape measurements in the formulas are in inches. If you measure in centimeters, the calculator converts them for you.

For most people, the Navy method lands within about plus or minus 3-4 percentage points of a DEXA scan, which is the laboratory reference method. That is why this calculator shows a realistic range around your result instead of a single false-precise number. Read the range, not just the headline figure, and judge progress by the trend over weeks.

Body Fat Categories

Use the table below to see where your body fat percentage falls. The ranges come from the American Council on Exercise and are widely used in fitness and health settings.

CategoryMenWomen
Essential fat2-5%10-13%
Athletes6-13%14-20%
Fitness14-17%21-24%
Average18-24%25-31%
Obese25%+32%+

These ranges follow the American Council on Exercise (ACE) chart, which groups body fat into essential fat, athletes, fitness, average, and obese. Essential fat is the minimum your body needs for hormones, insulation, and organ protection. The athlete and fitness bands are common targets for people who train regularly, while the average band covers typical healthy adults.

A category is a guide, not a verdict. Age, muscle mass, and fat distribution all affect what a given percentage looks like on your body. If your result sits near a boundary, the realistic range shown by the calculator matters more than the label.

How to Measure Correctly

Your result is only as good as your tape measurements. Follow these steps for a consistent reading:

  • Neck: measure just below the Adam’s apple, with the tape sloping slightly downward toward the front. Keep your shoulders relaxed and look straight ahead.
  • Waist: men measure at the navel, with the belly relaxed and the tape level around the body. Women measure at the narrowest point of the waist, usually just above the navel.
  • Hips: women measure at the widest point around the buttocks, with feet together and the tape level.
  • Tape tension: pull the tape snug against the skin without compressing it. The tape should lie flat, with no gaps and no pinching.
  • Measure twice and average: take each measurement twice and use the average. If the two readings differ by more than 1 cm, take a third.
  • Morning before eating: measure in the morning before eating, after using the bathroom. Food and water bloat the waist and shift the reading.

Worked Example

Here is a worked example using the default values in this body fat percentage calculator. A 30-year-old man is 175 cm tall, weighs 75 kg, and measures a 38 cm neck and an 88 cm waist.

Converted to inches, that is a 68.9 inch height, a 15.0 inch neck, and a 34.6 inch waist. The Navy formula gives a body fat percentage of 19.3%, with a realistic range of 16-22% and a category of Average. His fat mass is 14.5 kg, his lean mass is 60.5 kg, and his BMI is 24.5.

If he repeats the measurement in a month with the same technique and the result drops to 18%, that is real progress, even if the scale has barely moved, because it means he has lost fat while keeping his muscle.

Common Body Fat Calculator Problems (And How to Fix Them)

This body fat percentage calculator is a simple tool, and most wrong answers come from the measurements or the method, not the math. Here are the five problems we see most often, and how to fix each one.

  1. Three scales give three different numbers. BIA scales estimate fat from electrical resistance, which swings with hydration, food, and skin temperature. Spreads of 8+ points between devices are normal. Use one method and track the trend instead of comparing devices.
  2. Waist reads different every time. Tape placement, tension, and time of day all change the reading. Use the same spot, the same tension, and the same time of day, measure twice, and average the two readings.
  3. Calculator says one thing, but I look different. The Navy method assumes average fat distribution. Very lean, very muscular, or atypically shaped bodies fall outside that assumption, so the formula can miss. Treat the result as a range and consider a DEXA scan if you need precision.
  4. Wrong gender setting. The male and female formulas are completely different, and the female formula needs a hip measurement. Double-check the gender setting before you press Calculate, and make sure the hips field is filled in for women.
  5. Measured after a big meal. Food and water bloat the waist and push the result up. Measure in the morning before eating for a consistent baseline.

What To Do With Your Result

If the result from this body fat percentage calculator is in the Average or Obese band, a modest calorie deficit plus strength training is the most reliable path to a lower body fat percentage. Eating enough protein protects muscle while you lose fat, so the weight you drop comes mostly from fat.

Start with the calorie deficit calculator to set your daily intake, then use the macro calculator to split those calories into protein, carbs, and fat. If you train hard, the protein intake calculator will fine-tune your daily protein target.

If your result is already in the Fitness or Athletes band, your goal may be maintenance or a slow recomposition rather than fat loss. Re-measure every 2-4 weeks and adjust only when the trend is flat for a month.

Frequently Asked Questions

How accurate is this body fat percentage calculator?

Within about plus or minus 3-4 percentage points of a DEXA scan for most people. Read your result as a range, not an exact number, and trust the trend over weeks more than any single reading.

What is a healthy body fat percentage?

For general health, roughly 10-20% for men and 18-28% for women. See the ACE category table on this page for the full breakdown from essential fat to obese.

Why does my smart scale give a different number?

Smart scales estimate fat from electrical resistance, which swings with hydration. Three different scales can disagree by 8 points or more. A tape measurement plus a consistent trend is more reliable.

Can I use this if I am very muscular?

The Navy method can underestimate body fat in very muscular or very lean people, because it assumes average fat distribution. A DEXA scan is better in that case.

How often should I measure?

Every 2-4 weeks, in the morning before eating, with the same technique. Daily measurements mostly capture water and food noise.

Does age affect the result?

The formula does not use age, but fat distribution shifts as you age. Compare your own trend over time rather than judging one reading against a younger person’s numbers.

Why is my waist measurement different each time?

Tape placement and tension change the reading. Use the same spot, the same tension, measure twice and average.

What is the difference between body fat % and BMI?

BMI is weight divided by height squared and cannot tell fat from muscle. Body fat percentage measures your actual composition: how much of your weight is fat versus lean mass.

What should I do if my body fat is too high?

Aim for a modest calorie deficit, protein at 1.6-2.2 g/kg, and strength training to protect muscle. The calorie deficit calculator and macro calculator on this site will set the numbers for you.

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