Skinfold Body Fat Calculator

Free Skinfold Body Fat Calculator (Caliper Method)

This skinfold body fat calculator turns a handful of caliper readings into a real body fat percentage in seconds. Pick your test — 3-site, 4-site, or 7-site — enter your age and the skinfold measurements in millimeters or inches, and you'll instantly see your body fat percentage, your estimated body density, your category, and, if you add your weight, your fat mass and lean mass too.

Skinfold testing has been used by coaches, trainers, and gym staff for decades because it needs nothing more than a pair of skinfold calipers and a few minutes. It's cheap, it's repeatable, and once you know the technique, it gives a far more useful number than a bathroom scale, which can't tell fat from muscle.

What Is a Skinfold Test, and How Does It Work?

A skinfold test measures the thickness of the fat layer just under your skin at a handful of specific spots on your body. A trained hand pinches the skin and the fat beneath it away from the muscle, and a caliper — a simple spring-loaded tool — clamps the fold and reads its thickness in millimeters.

Because roughly half of the body's total fat sits directly under the skin, these subcutaneous readings correlate closely with total body fat. Add up the readings from several sites, run the sum through a validated formula, and you get an estimate of body density, which then converts into a body fat percentage using either the Siri or Brozek equation. This calculator shows both, side by side, so you can compare them directly.

Choosing a Test: 3-Site vs 4-Site vs 7-Site

This calculator supports three well-known skinfold protocols, and you can switch between them freely to compare results.

• 3-Site (Jackson-Pollock): the fastest option. Men measure chest, abdomen, and thigh; women measure triceps, suprailiac, and thigh. Great for quick, regular check-ins.
• 4-Site (Durnin-Womersley): measures biceps, triceps, subscapular, and suprailiac for both sexes. Uses a slightly different equation based on the log of the total, with coefficients that shift by age band.
• 7-Site (Jackson-Pollock): the most thorough option, adding midaxillary and taking chest, triceps, subscapular, abdomen, suprailiac, and thigh together for both sexes. Generally considered the most accurate of the three because it averages out any single bad reading across more sites.

How to Take Skinfold Measurements Correctly

The formula is only as good as the measurements you feed it, and skinfold technique takes a little practice to get consistent. A few basics make a big difference.

• Pinch the skin and fat firmly with your thumb and index finger, keeping the fold separate from the muscle underneath.
• Place the caliper jaws about 1cm below your fingers, at the midpoint of the fold, and let go of the caliper handle before reading.
• Wait about 2 seconds after the caliper closes before recording the number, since the reading settles slightly as fat compresses.
• Take each site 2-3 times and use the average, rather than trusting a single pinch.
• Always measure on the right side of the body, which is the standard convention used in almost every published formula.
• Measure at the same time of day, ideally before exercise, since fluid shifts during workouts can temporarily change skinfold thickness.

Where Each Skinfold Site Is Located

Getting the exact spot right matters as much as the pinch itself. Here's where to find each site this calculator can use, depending on which test and sex you select.

• Chest: a diagonal fold halfway between the armpit and the nipple (men) or one-third of the way from the armpit to the nipple (women).
• Midaxillary: a vertical fold on the side of the body, in line with the armpit, at the level of the bottom of the sternum.
• Triceps: a vertical fold on the back of the upper arm, halfway between the shoulder and elbow.
• Subscapular: a diagonal fold just below the bottom tip of the shoulder blade.
• Abdomen: a vertical fold about 2cm to the right of the navel.
• Suprailiac: a diagonal fold just above the hip bone, following the natural line of the pelvis.
• Thigh: a vertical fold on the front of the thigh, halfway between the hip and the top of the kneecap.
• Biceps: a vertical fold on the front of the upper arm, directly above the triceps site.

Understanding Body Density and the Siri Formula

Every skinfold formula on this page has the same two-step logic. First, it estimates your body density — how tightly packed your body mass is — from the sum of your skinfold readings and your age. Fat tissue is less dense than lean tissue, so a lower body density generally points to a higher body fat percentage.

Second, that body density is converted into an actual body fat percentage using a population-based equation. The most common one is the Siri formula, published in 1961, and this calculator uses it as the headline number. We also show the slightly older Brozek formula from 1963 alongside it, since the two occasionally differ by half a percentage point or so, and seeing both gives you a useful sanity check.

Reading Your Body Fat Category

Once your body fat percentage is calculated, this tool places you into one of five bands: Essential Fat, Athletic, Fitness, Average, or Obese. The chart above shows exactly where you land, with separate ranges for men and women, since women naturally carry more essential fat for hormonal and reproductive reasons.

Essential fat is the fat every body needs just to function, so dropping below it is a health risk, not a fitness milestone. The Athletic and Fitness bands describe lean, active bodies, Average is where most adults fall, and the Obese band is worth discussing with a doctor, ideally alongside other health markers rather than in isolation.

Fat Mass and Lean Mass: Turning a Percentage Into Real Numbers

Add your weight and this calculator unlocks two extra figures: fat mass, the actual kilograms or pounds of fat on your frame, and lean mass, everything else — muscle, bone, organs, and water. These numbers matter because a percentage alone doesn't tell you whether your weight is changing due to fat loss, muscle loss, or both.

Tracking fat mass and lean mass over weeks or months gives a far clearer picture than the scale by itself. If your fat mass is trending down while lean mass holds steady, that's a strong sign a training and nutrition plan is working exactly as intended.

How Accurate Is the Skinfold Method?

In the hands of an experienced tester, skinfold measurements typically land within about 3 to 4 percentage points of a lab-grade result like hydrostatic weighing or a DEXA scan, which is a solid result for a technique that only needs a caliper and a tape measure. That accuracy depends heavily on consistent technique, though, and it drops noticeably when different people take the measurements, or when the same person measures inconsistently over time.

The 7-site protocol tends to be the most reliable of the three offered here, simply because averaging across more locations smooths out the effect of any single site being pinched slightly wrong. If you're new to skinfold testing, expect your first few sessions to be less consistent than later ones, once your technique settles.

Skinfold Calipers vs Other Body Fat Methods

Bioelectrical impedance scales are convenient but swing wildly with hydration level, meal timing, and even how long you've been standing. DEXA scans and hydrostatic (underwater) weighing are the most accurate options available, but they require expensive equipment and a lab visit, which most people simply don't have regular access to.

Skinfold testing sits in a practical middle ground: more consistent than a bioelectrical scale, far cheaper and more accessible than a DEXA scan, and precise enough to track real progress over time when the same person measures you the same way each time. That's exactly why it remains the go-to method for coaches and trainers doing regular body composition check-ins.

Tips to Get Consistent Results Every Time

A little consistency goes a long way with skinfold testing, and these habits will keep your numbers comparable from one check-in to the next.

• Have the same person take your measurements each time if possible, since technique varies from tester to tester.
• Mark the exact measurement spots the first time, so you can find them again quickly next time.
• Retest every 3-4 weeks rather than every few days — meaningful body composition change takes time to show up.
• Avoid testing right after a workout, sauna, or hot shower, since increased blood flow can temporarily change skinfold thickness.
• Keep the caliper calibrated and replace it if the spring tension feels noticeably different from when it was new.

Limitations of the Skinfold Body Fat Method

No field method is perfect, and skinfold testing has known limits worth understanding. It assumes fat is distributed in a fairly typical pattern across the body, so it can be less accurate for people with very high or very low body fat, or unusual fat distribution. It also depends entirely on tester skill, which is why home results between two different testers can vary more than expected.

Treat the number this calculator gives you as a solid, low-cost estimate for tracking your own trend over time, not a clinical diagnosis. If you need a lab-grade number for medical reasons, ask your doctor about a DEXA scan or hydrostatic weighing instead.

Who Should Use a Skinfold Body Fat Calculator

This tool is a great fit for gym-goers, athletes, and coaches who already own calipers and want a fast way to convert raw readings into a real percentage without doing the math by hand. It's equally useful if you're new to body composition tracking and want a low-cost, repeatable baseline before starting a training or nutrition program.

Because it supports three different protocols side by side, it also works well if you're comparing results from an old gym assessment against a newer one, or checking how the 3-site and 7-site numbers line up for your own body.

Advanced Features Built Into This Calculator

This isn't a basic one-formula tool. You can switch between three validated skinfold protocols on the fly, and the site fields update automatically to match whichever test and sex you pick, so you're never guessing which measurements to enter.

Every result comes with both the Siri and Brozek body fat percentages calculated side by side, plus your raw body density, so you can see exactly how the math got there instead of trusting a black box. Switch your skinfold readings between millimeters and inches at any time and every field converts instantly without losing your data.

Add your weight and the calculator immediately unlocks fat mass and lean mass in kilograms or pounds, so a single percentage turns into two concrete numbers you can track over time. The category chart updates live with every input change, showing exactly where your result sits against the Essential Fat, Athletic, Fitness, Average, and Obese bands for your sex, with a dashed marker pinpointing your exact percentage.

Skinfold Body Fat Calculator: Common Questions People Search

People land on this page searching for things like skinfold body fat calculator, skinfold caliper calculator, jackson pollock body fat calculator, durnin womersley calculator, or how to calculate body fat with calipers, because turning raw millimeter readings into a real percentage by hand is tedious and easy to get wrong. This calculator does that work instantly and privately, with no signup, no app download, and support for all three major skinfold protocols in one place.