Body Fat Percentage

What you will need
  • A flexible body measuring tape (in cm or inches).
  • A mirror or a friend to help keep the tape level around your neck, waist and hips.

Take measurements on bare skin. The tape should be snug but not digging in or compressing the tissue.

What you will need
  • A skinfold caliper calibrated in millimetres (mm).
  • A mirror or a training partner to help you find each site.
  • Pen/paper or your phone to record each of the 7 readings.

Take all measurements on the same side of the body (usually the right), on dry skin, when you are relaxed - not straight after a very hard workout or hot shower.

How this calculator works

Learn what this method measures, which formula is used, and how to interpret your result.

What it measures

Circumference Pro estimates your body fat using simple tape measurements. It mainly reflects subcutaneous fat distribution around your waist/hip relative to height and neck size.

How to measure correctly

  • Measure on bare skin with the tape snug (not compressing).
  • Keep the tape level (use a mirror).
  • Take 2–3 readings and use the average.
  • Waist: exhale normally — don’t suck in.

Formula used (US Navy)

Uses log10 equations based on height and circumferences.

Men: %BF = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76
Women: %BF = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387

Accuracy & limitations

  • It’s an estimate — tape placement and posture can shift results.
  • Less reliable for people with unusual fat distribution or very high muscularity.
  • Food volume, bloating, and hydration can slightly affect waist measurements.

How to interpret your result

Use your %BF to track trends (every 2–4 weeks) rather than obsessing over single readings. Combine this with strength, energy, sleep quality, and progress photos.

Best for: quick tracking Equipment: tape Time: 2 minutes

Mini FAQ

How accurate is this body fat % estimate?

It’s a useful estimate, but accuracy depends on the method you use and how well the inputs match your body. Tape-based methods can be solid for tracking trends, but they can be off for some people due to fat distribution, posture, and measurement technique.

Why is my result different from a DEXA scan or smart scale?

Different tools estimate body fat differently. DEXA, calipers, bio-impedance scales, and tape formulas all rely on different assumptions. Hydration, food intake, and even skin temperature can shift scale readings. The best approach is to stick to one method and track changes over time.

Where exactly should I measure?

Use consistent landmarks every time. Common spots are: waist (around navel or narrowest point—use the same one each time), neck (just below the Adam’s apple), and hips (widest part of the glutes) if your method uses it. Measure relaxed, tape snug (not tight), and don’t suck in.

Should I measure in the morning or night?

For the most consistent tracking, measure in the morning after using the bathroom, before food, and before training. Night-time measurements can be higher due to food, water, and swelling.

How often should I re-check my body fat %?

Weekly is usually plenty. Daily readings can be noisy. If you want tighter tracking, do 2–3 measurements each time and use the average.

Have more questions? Visit the full FAQs.

Next step: copy your body fat % into the BMR & TDEE calculator to estimate your basal metabolic rate (BMR)

What it measures

Skinfold Pro estimates your body fat by measuring subcutaneous fat thickness at 7 standard sites. This is often more sensitive to small changes than tape methods.

How to measure correctly

  • Measure on the same side of the body (usually right).
  • Pinch skin + fat (not muscle), place caliper ~1 cm below fingers.
  • Read after 1–2 seconds (don’t wait too long).
  • Take 2–3 readings per site and use the average.

Formulas used (JP-7 + Siri)

First we estimate body density using Jackson–Pollock 7-site equations. Then we convert density to body fat % using the Siri equation.

Body density: sex + age + sum of 7 skinfolds → density
Siri: %BF = (495 / density) − 450

Accuracy & limitations

  • Accuracy depends heavily on site location and caliper technique.
  • Different calipers can read slightly differently — try to use the same one.
  • Best used to track trends, not as a perfect “true” number.

How to interpret your result

For the best tracking: measure at the same time of day, same hydration level, and avoid measuring immediately after a hard workout or hot shower.

Best for: detailed tracking Equipment: calipers Time: 8–12 minutes

Mini FAQ

How accurate is this body fat % estimate?

It’s a useful estimate, but accuracy depends on the method you use and how well the inputs match your body. Tape-based methods can be solid for tracking trends, but they can be off for some people due to fat distribution, posture, and measurement technique.

Why is my result different from a DEXA scan or smart scale?

Different tools estimate body fat differently. DEXA, calipers, bio-impedance scales, and tape formulas all rely on different assumptions. Hydration, food intake, and even skin temperature can shift scale readings. The best approach is to stick to one method and track changes over time.

Where exactly should I measure?

Use consistent landmarks every time. Common spots are: waist (around navel or narrowest point—use the same one each time), neck (just below the Adam’s apple), and hips (widest part of the glutes) if your method uses it. Measure relaxed, tape snug (not tight), and don’t suck in.

Should I measure in the morning or night?

For the most consistent tracking, measure in the morning after using the bathroom, before food, and before training. Night-time measurements can be higher due to food, water, and swelling.

How often should I re-check my body fat %?

Weekly is usually plenty. Daily readings can be noisy. If you want tighter tracking, do 2–3 measurements each time and use the average.

Have more questions? Visit the full FAQs.

Next step: use your estimated body fat % to improve your calorie targets in BMR & TDEE.

Explore other tools