FFMICALCULATORE.COM / COMPOSITION INDEX

Body Fat Calculator tape measure, no expensive scans needed.

Free body fat percentage calculator using the U.S. Navy Method, the most accurate tape-based formula validated against hydrostatic weighing. Enter four measurements, get your number in seconds.

BODY FAT / NAVY METHOD ● LIVE

01 /Input Parameters

AgeYEARS

HeightCM

WeightKG

NeckCM

WaistCM

[?] How to measure correctly →

Neck: measure just below the larynx (Adam's apple), tape level all the way around.
Waist: men measure at navel level. Women measure at the narrowest point between ribs and hip. Stand relaxed at end of normal exhale.
Hip (women only): measure at the widest point of buttocks, tape level.
Use a flexible cloth tape, snug but not tight.

02 /Output / Verdict

// AWAITING INPUT

Fill in your measurements on the left and run the analysis to view your body fat report.

01U.S. Navy formula

02Fat & lean mass

03Gender-specific

04No data tracking

What Is Body Fat Percentage?

Body fat percentage is the proportion of your total body weight that is made up of fat tissue, expressed as a percent. A 80 kg person with 15% body fat carries 12 kg of fat and 68 kg of lean tissue (muscle, bone, organs, water). It is the single most useful body composition number for athletes, lifters, and anyone who cares about how their body is actually built rather than just what the scale says.

Unlike BMI, which only knows weight and height, body fat percentage tells you the truth about your composition. Two people at the same weight and height can have wildly different fat percentages, and those differences correspond to wildly different health profiles, athletic capacities, and visual physiques.

This Body Fat Calculator uses the U.S. Navy circumference method, validated against hydrostatic weighing, to estimate your body fat from a tape measure and a few inputs. No scans, no calipers, no monthly subscription.

The U.S. Navy Body Fat Formula

The Navy method was developed in the 1980s for military fitness assessment and has been refined through decades of research. It uses circumference measurements at specific anatomical landmarks to estimate body density, then converts that to fat percentage.

MEN (metric):
BF% = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450

WOMEN (metric):
BF% = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450

The formulas look intimidating but the calculator above does the math instantly. The accuracy of the result depends entirely on the accuracy of your tape measurements, which is why getting them right matters.

Body Fat Measurement Methods Compared

The Navy method is one of several ways to estimate body fat. Each has tradeoffs in accuracy, cost, and accessibility.

Tier A
Best

DEXA Scan, Hydrostatic Weighing, Bod PodAccuracy within 1 to 3%. Clinical gold standards. Cost $50 to $150 per scan. Use once or twice yearly for baseline measurements.

Tier B
Good

Skinfold Calipers (Trained Tester)Accuracy within 3 to 5%. Affordable, portable, repeatable. Best when measured by an experienced tester at consistent landmarks.

Tier B
Good

U.S. Navy Tape Method (this calculator)Accuracy within 3 to 5% for most adults. Free, requires only a tape measure. Slightly less accurate at the extremes of body composition.

Tier C
Avoid

Bioelectrical Impedance ScalesAccuracy often 5 to 10% off. Readings swing with hydration, time of day, and recent meals. Not reliable for serious tracking.

How to Measure Yourself Correctly

Your body fat number is only as accurate as your tape measurements. A 1 cm error on the waist can shift the result by 1 to 2%. Use a flexible cloth tape, measure first thing in the morning before eating or drinking, and keep the tape level and snug without compressing the skin.

01 / NECK

Just Below Larynx

Wrap the tape around the neck just below the larynx (Adam's apple for men). Keep the tape horizontal. Stand naturally, do not flex or strain. Record to the nearest 0.1 cm.

02 / WAIST

Navel or Narrowest

Men: measure at the level of the navel. Women: measure at the narrowest part of the torso between ribs and hips. Stand relaxed at the end of a normal exhale. Tape level, not pulled tight.

03 / HIP

Widest Buttocks (Women)

Women only. Measure around the widest point of the buttocks with feet together. Tape horizontal, snug but not compressing tissue. Take the measurement standing, not sitting.

Tip: Take each measurement three times and use the average. Tape measurements have natural variability of about 0.5 cm even with careful technique. Averaging removes random error.

Body Fat Categories for Men

Male body fat ranges run lower than female ranges due to hormonal differences. The American Council on Exercise classification is the most widely cited standard.

Body Fat %	Category	Description
2 to 5%	Essential Fat	Minimum required for survival, contest-stage bodybuilder territory
6 to 13%	Athlete	Visible abs and vascularity, lean and muscular look
14 to 17%	Fitness	Athletic but softer, abs visible in good lighting
18 to 24%	Average	Typical untrained adult male
25 plus	Obese	Elevated metabolic and cardiovascular risk

Body Fat Categories for Women

Female body fat ranges run higher than male because women carry essential fat for reproductive function. Going below 12 to 14% can disrupt menstrual cycles and hormone production.

Body Fat %	Category	Description
10 to 13%	Essential Fat	Minimum required for survival, often unsustainable long-term
14 to 20%	Athlete	Lean and athletic, visible muscle definition
21 to 24%	Fitness	Toned and healthy, soft definition visible
25 to 31%	Average	Typical untrained adult woman
32 plus	Obese	Elevated metabolic and cardiovascular risk

The scale tells you what you weigh. Body fat tells you what kind of weight it is. Same number, two completely different stories. FFMICALCULATORE.COM / EDITORIAL

How to Use This Body Fat Calculator

Pick Units & Gender

Select metric or imperial, then choose male or female. The hip field appears for women.

Enter Stats

Input age, height, and weight. Weight is used to calculate fat mass and lean mass.

Add Measurements

Enter neck and waist (and hip if female). Follow the measurement guide for accuracy.

Run Analysis

Tap Run Analysis. Your body fat percentage, category, fat mass, and lean mass appear instantly.

Worked Example: Calculate Body Fat Step by Step

Here is a full Navy method calculation for a male athlete with realistic measurements.

Inputs (Male) Height: 180 cm
Weight: 80 kg
Neck: 38 cm
Waist: 85 cm

Calculate Waist minus Neck 85 − 38 = 47 cm
log10(47) = 1.6721

Calculate log10(Height) log10(180) = 2.2553

Apply Navy Formula Den = 1.0324 − 0.19077 × 1.6721 + 0.15456 × 2.2553
Den = 1.0324 − 0.3190 + 0.3486 = 1.0620
BF% = 495 / 1.0620 − 450 = 16.1%

Calculate Fat & Lean Mass Fat Mass = 80 × 0.161 = 12.9 kg
Lean Mass = 80 − 12.9 = 67.1 kg

VERDICT: A body fat percentage of 16.1% places this athlete in the Fitness range. He carries 67.1 kg of lean mass and 12.9 kg of fat. To reach Athlete category (under 14%), he would need to lose roughly 2 kg of fat.

How to Lower Your Body Fat Percentage

Lowering body fat percentage requires losing fat while preserving muscle. Doing it without losing muscle is the hard part. The fundamentals are simple even if execution is not.

Nutrition

Run a moderate caloric deficit of 300 to 500 calories below maintenance daily
Hit 2.0 to 2.4 grams of protein per kg of bodyweight to protect lean mass during the cut
Prioritize whole foods. Aim for 80% nutrient-dense foods and 20% flexibility
Eat 25 to 35 grams of fiber daily for satiety and digestion
Hydrate properly. Aim for 35 ml per kg of bodyweight

Training

Lift weights at least 3 to 5 times per week with progressive overload
Focus on compound movements: squat, deadlift, bench press, row, pull-up, overhead press
Do not reduce training intensity during a cut. Keep loads heavy
Add 150 to 300 minutes of moderate cardio per week, ideally low impact
Sleep 7 to 9 hours nightly. Recovery drives fat loss as much as training does

Realistic Timelines

Sustainable fat loss happens at 0.5 to 1% of bodyweight per week. Faster than that and you are losing muscle. Expect to lose 0.5 to 1 percentage point of body fat per month with consistent effort. Going from 20% to 12% might realistically take 8 to 16 months for a natural lifter. Patience is the hardest macronutrient.

Frequently Asked Questions

What is a healthy body fat percentage?+

For men, a healthy range is roughly 14 to 24%. For women, 21 to 31%. Athletes typically sit lower (men 6 to 13%, women 14 to 20%). Going below the essential fat threshold (5% men, 13% women) is generally unsustainable and can disrupt hormonal function.

How accurate is the U.S. Navy body fat method?+

The Navy method is accurate within 3 to 5% for most adults when measurements are taken correctly. It tends to slightly overestimate body fat in very lean athletes and slightly underestimate in obese individuals. For most users it is the best free measurement-based option available.

What is the most accurate body fat measurement method?+

DEXA scan is considered the gold standard for clinical accuracy, typically within 1 to 2%. Hydrostatic weighing and Bod Pod are similarly accurate. These methods cost $50 to $150 per scan. The Navy method offers the best accuracy among free options.

Why is body fat different for men and women?+

Women carry more essential body fat than men due to reproductive and hormonal requirements. The female body needs roughly 10 to 13% essential fat for normal cycles and hormone production, compared to 2 to 5% for men. This is biological, not a fitness deficit.

How often should I measure body fat?+

Once every 2 to 4 weeks is plenty. Body fat changes slowly, and weekly measurements add noise without signal. Take measurements at the same time of day, fasted if possible, after using the bathroom. Average three readings per session for accuracy.

Can I lose body fat without losing muscle?+

Yes. The keys are a moderate caloric deficit (not aggressive), high protein intake (2 to 2.4 g/kg), continued strength training with heavy loads, and adequate sleep. Aim for 0.5 to 1% bodyweight loss per week. Faster cuts almost always cost muscle.

Is body fat the same as BMI?+

No. BMI uses only height and weight and cannot tell muscle from fat. Body fat percentage isolates fat tissue from lean mass. A muscular athlete and a sedentary person can share the same BMI but have radically different body fat percentages and health profiles.

What is the lowest safe body fat percentage?+

Long-term sustainable lows are roughly 6% for men and 14 to 16% for women. Bodybuilders dip lower for contests but cannot maintain those levels. Going below essential fat (5% men, 13% women) for extended periods risks hormonal disruption, immune suppression, and other health issues.

Is the Body Fat Calculator free?+

Yes. The Body Fat Calculator at ffmicalculatore.com is completely free, requires no signup, and runs entirely in your browser. None of your inputs are stored, transmitted, or tracked.