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Free · Body Composition · Instant

Body Weight Calculator

Go beyond the number on the scale — estimate your body fat percentage and lean mass, then track your weight trend smoothed to filter out normal day-to-day fluctuations.

✓ Free Forever ✓ Navy Method Body Fat ✓ Smoothed Trend Tracker

Body Composition Calculator

Measure with a soft tape at the narrowest/widest points described in our Measurement Guide below.

Please fill in all required fields with valid values.

Bonus Tool

Weight Trend Tracker (Smoothed)

Your weight naturally fluctuates day to day due to water, food, and sodium — not just fat. Log a few entries and we'll calculate a moving average to reveal your real trend.

Entry #Weight (kg)Moving AverageTrend
Add at least 3 entries to see your smoothed trend.
3-Entry Moving Average Trend --
The Science

How We Calculate Body Composition

Quick Estimate (Deurenberg Formula, BMI-Based)

Body Fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) − 5.4 sex = 1 for male, 0 for female

Navy Method (Circumference-Based)

Men: BF% = 495 / (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450 Women: BF% = 495 / (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.22100×log₁₀(height)) − 450

Lean & Fat Mass

Fat Mass = Weight × (Body Fat % ÷ 100) Lean Mass = Weight − Fat Mass
Worked Example

Step-by-Step Example (Navy Method)

A 30-year-old male, 178 cm tall, 85 kg, with a 38 cm neck and 90 cm waist.

1
Waist − Neck: 90 − 38 = 52 cm
2
Apply Navy formula: using log₁₀(52) and log₁₀(178) → BF% ≈ 18.4%
3
Fat mass: 85 × 0.184 ≈ 15.6 kg
4
Lean mass: 85 − 15.6 = 69.4 kg
Reference

Body Fat Percentage Categories

Based on the American Council on Exercise classification.

CategoryMenWomen
Essential Fat2-5%10-13%
Athletes6-13%14-20%
Fitness14-17%21-24%
Average18-24%25-31%
Obese25%+32%+
How To Measure

Getting Accurate Circumference Measurements

1
Neck: measure just below the larynx (Adam's apple), tape sloping slightly downward to the front.
2
Waist: measure at the narrowest point, typically level with your navel, without pulling the tape tight.
3
Hip (women): measure at the widest point around your hips and buttocks.
4
Consistency matters: measure at the same time of day (ideally morning, before eating) for comparable results over time.
Who Uses This

Common Ways People Use This Calculator

🏋
Healthy Weight Goals
Estimate a healthy body weight for your height.
💪
Fitness Planning
Set realistic weight targets for exercise programs.
📈
Weight Management
Monitor progress while gaining or losing weight.
🩺
General Health
Compare your weight with commonly used healthy ranges.
🎓
Students
Learn how height and body weight are related.
👨‍⚕️
Healthcare Support
Use estimated weight values during health assessments.
👟
Lifestyle Tracking
Keep an eye on long-term weight changes.
🎯
Personal Goals
Plan achievable weight milestones with confidence.
Get More From It

Tips for Accurate Weight Tracking

Weigh Yourself Consistently

Measure your weight at the same time each day, ideally in the morning before eating or drinking.

Wear Similar Clothing

Use lightweight or consistent clothing when weighing yourself to improve accuracy over time.

Use the Same Scale

Different scales may produce slightly different readings, so stick with one reliable scale.

Focus on Long-Term Trends

Daily weight naturally fluctuates due to hydration, meals, and activity. Monitor weekly or monthly trends instead.

Track Height Changes for Children

Growing children should update both height and weight regularly for more meaningful results.

Combine with a Healthy Lifestyle

Use your weight estimate as a guide alongside balanced nutrition, regular exercise, and advice from healthcare professionals.

Guides

Guides and charts

The US Navy body fat formulaThe US Navy body fat formula estimates body fat % from height, neck, waist and hip measurements. Body fat percentage chartBody fat percentage chart for men and women with ACE categories (essential, athletes, fitness, average, obese), plus waist cut-offs for Indians.. How to measure your waist, neck and hipsStep-by-step instructions to measure your neck, waist and hips correctly with a tape for the Navy body fat method, and the mistakes to avoid..
India guidelines

Waist size and body fat: Indian cut-offs

Asian Indians tend to store more fat around the abdomen at a lower body weight, so Indian guidelines use waist size and BMI cut-offs that are lower than the international ones.

MeasureInternationalAsian Indian guidelines
Abdominal obesity, men (waist)Above 102 cmAbove 90 cm
Abdominal obesity, women (waist)Above 88 cmAbove 80 cm
Overweight (BMI)25.0 – 29.923.0 – 24.9
Obesity (BMI)30 and above25 and above

Measure your waist at the level of your navel, standing relaxed, after breathing out. The Navy method on this page already uses your waist, so tracking it over time is useful even when the scale does not move.

Sources

  1. Consensus statement on obesity and metabolic syndrome for Asian Indians (Misra A. et al., J Assoc Physicians India, 2009), summary on PubMed Central
  2. Abdominal obesity in Indians: waist circumference cut-offs (Centre for Diabetes, Obesity and Cholesterol research summary)
  3. WHO Expert Consultation: Appropriate body-mass index for Asian populations (The Lancet, 2004)

Last reviewed on 25 October 2026 by the editorial team at Evavel Private Limited. Found an error? Email care@calculations.one.

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Questions

Frequently Asked Questions

The Navy Method is generally more accurate since it uses actual body measurements rather than BMI alone, which doesn't account for body shape or fat distribution.
Navy Method typically has an error margin of about 3-4% compared to DEXA scans (the clinical gold standard), which is reasonable for a free at-home method but not lab-precise.
Daily weight fluctuates due to water retention, sodium intake, and digestion — often by 1-2 kg — which can mask your real progress. A moving average smooths this out to show the underlying trend.
At least 3 entries for a basic moving average, though 7 or more (ideally daily) gives a much clearer, more reliable trend line.
Lean body mass is your total body weight minus fat mass — it includes muscle, bone, organs, and water. Preserving lean mass during weight loss is generally a fitness goal.
Yes — falling below essential fat levels (roughly 2-5% for men, 10-13% for women) can impair hormone function and overall health. Very low body fat should be approached under professional guidance.
The Navy Method tends to be more reliable than BMI-based estimates for muscular individuals, since it doesn't penalise extra muscle weight the way BMI does — though it can still be imperfect for extreme physiques.
Monthly is typically sufficient, since body composition changes gradually — measuring more frequently mostly captures measurement noise rather than real change.
No. All calculations, including your Weight Trend Tracker entries, run entirely in your browser for this session — nothing is sent to or stored on our servers.
Men and women tend to store fat differently (more abdominally for men, more in hips for women), so the formula uses hip circumference for women in addition to waist and neck to account for this.
Yes — use "Quick Estimate" mode, which only requires your height, weight, age, and gender. It's less precise than the Navy Method but requires no measurements.
No. Conditions like thyroid disorders, PCOS, or certain medications can affect both weight and body composition — consult a doctor if you have concerns about an underlying condition.
Treat any single reading as an estimate with some margin of error. Tracking the trend over several measurements gives a more reliable picture than one isolated number.
Many sources cite roughly 0.5-1% of body weight per week as a sustainable rate that helps preserve lean mass, though individual circumstances vary — consult a professional for personalised guidance.
Yes, the unit toggle applies to your circumference measurements as well — switch between centimetres and inches at any time before calculating.
No, entries are kept only for your current browser session. If you want a longer-term record, consider noting your moving average trend elsewhere each time you check it.

See Past the Scale

Calculate your body fat and lean mass above, then track your real trend over time.

✓ Navy Method ✓ Lean vs Fat Mass ✓ Smoothed Trend