Calculate your Body Mass Index and see your healthy weight range using metric or imperial units.
Formula: BMI = weight (kg) ÷ (height (m))². For imperial units: BMI = 703 × weight (lb) ÷ (height (in))².
Example: 70 kg, 1.75 m → BMI = 70 ÷ (1.75²) = 22.86
BMI, or Body Mass Index, is a simple screening test that uses your height and weight to place you into a category: underweight, normal, overweight, or one of three obesity classes. Enter your height in cm and weight in kg for the metric calculation, or feet/inches and pounds for imperial — the result is the same. It does not directly measure body fat, so it can misclassify muscular people and may underestimate risk in older adults. Despite its limits, BMI remains the standard first step because it is fast, free, and supported by decades of population data, and is also known as the body mass index test in clinical settings.
Body Mass Index (BMI) is a simple, widely-used screening tool that estimates body fat based on your height and weight. Developed in the 1830s by Belgian mathematician Adolphe Quetelet, BMI provides a quick way to categorize weight status and assess potential health risks.
This range is associated with the lowest risk of weight-related health problems. Maintaining a healthy BMI supports cardiovascular health, reduces diabetes risk, and promotes overall well-being.
This range indicates increased risk for conditions like high blood pressure, type 2 diabetes, and certain cancers. Modest weight loss (5-10%) can significantly improve health outcomes.
Obesity significantly increases risk for serious health conditions including heart disease, stroke, type 2 diabetes, and sleep apnea. Medical consultation is recommended for comprehensive management.
Being underweight can lead to nutritional deficiencies, weakened immune function, and osteoporosis. Focus on nutrient-dense foods and consult healthcare providers if unintentional weight loss occurs.
While BMI is useful for population-level assessments, it has significant individual limitations:
Professional Guidance: BMI is a screening tool, not a diagnostic instrument. Always consult with healthcare professionals for personalized health assessments and recommendations. Your overall health depends on many factors beyond BMI, including diet quality, physical activity, sleep, stress management, and genetic predispositions.
Type your weight (in kg or lbs) and height (in cm or inches). The calculator auto-converts to metric for the BMI formula.
BMI = weight in kg divided by height in meters squared. A 70 kg person who is 1.75 m tall has a BMI of 22.9.
Below 18.5 is underweight, 18.5-24.9 is normal, 25-29.9 is overweight, 30+ is obese. The calculator also shows the healthy BMI range for your height.
For related calculations, try our body fat calculator.
BMI is weight (kg) ÷ height (m)². For imperial: BMI = 703 × weight (lb) ÷ height (in)². The result falls into one of these standard adult categories:
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese — Class I |
| 35.0 – 39.9 | Obese — Class II |
| 40.0 and above | Obese — Class III (severe) |
Example: A 5'9" (175 cm) adult who weighs 170 lb (77 kg) has a BMI of 25.1 (just over the normal range). A 5'4" (163 cm) adult who weighs 140 lb (63.5 kg) has a BMI of 23.9 (normal weight).
BMI is a screening tool, not a diagnosis. It does not directly measure body fat, so muscular athletes may register as overweight or obese despite low body fat. For a fuller picture, use BMI alongside body-fat percentage and waist circumference.
The metric BMI formula was developed by Adolphe Quetelet in the 1830s and adopted as “body mass index” by Ancel Keys in 1972:
BMI (metric) = weight (kg) ÷ height (m)² BMI (imperial) = 703 × weight (lb) ÷ height (in)²The constant 703 is the exact unit-conversion factor: (1 kg / 2.2046 lb) × (39.3701 in/m)² = 703.0.
Worked example (the 5'9" / 170 lb number above):
weight = 170 lb, height = 69 in BMI = 703 × 170 ÷ 69² = 119,510 ÷ 4,761 = 25.10The same person in metric (77 kg, 1.75 m) computes to 77 ÷ 1.75² = 25.14 — a 0.04 difference from rounding, which is why you may see slightly different BMI values reported in different tools.
For children and teens (ages 2–20), the calculator logic changes: BMI is plotted on age- and sex-specific growth charts, and the result is a percentile, not a category. CDC's BMI percentile tool is the reference for that age group.
BMI has well-documented blind spots. It cannot tell fat from muscle, which produces misleading results for:
Use BMI as a starting point, then add body fat percentage and waist circumference for a complete picture.
Daniel is 35, 5'11" (180 cm), and starts at 210 lb (95 kg). His initial BMI:
BMI = 95 ÷ 1.80² = 29.3 (just under obese Class I)He walks 30 minutes a day, cuts 500 kcal/day, and after 6 months weighs 185 lb (84 kg):
BMI = 84 ÷ 1.80² = 25.9 (overweight, but trending down)After another 4 months he hits 175 lb (79 kg):
BMI = 79 ÷ 1.80² = 24.4 (normal weight)Daniel's BMI went from 29.3 → 24.4 — a 5-point drop over 10 months — without extreme dieting. This is the kind of gradual, sustainable change BMI is good at tracking.
Calculator formulas follow the standard metric (kg/m²) and imperial (703 × lb/in²) equations and are consistent with WHO and CDC clinical guidance.
Every CalcCentral calculator is authored by a credentialed subject-matter expert and independently reviewed before publication. Our editorial policy follows the same E-E-A-T guidelines used by Google to evaluate YMYL (your-money-or-your-life) pages.
Author
Dr. Aaron Pak, PhD
Doctor of Kinesiology & Public Health
Independently reviewed
Jonathan Reed, MS
Master of Applied Mathematics
Last reviewed: August 12, 2026 · Next scheduled review: quarterly
BMI Calculator is available as a free, lightweight widget. Add a quick BMI check to your fitness, nutrition, or wellness posts. Works with metric and imperial inputs. Copy a single iframe snippet into your blog post.
Ideal for: Health blogs, fitness sites, wellness publishers.
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Each calculator includes the formula, plain-English explanation, and FAQs so you understand the result.
Estimates only. Calculator results are for educational and planning purposes — not professional advice. For binding decisions on taxes, investments, health, or legal matters, consult a qualified professional.
FAQ
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A BMI calculator for guys is a tool that computes body mass index using male-specific reference ranges and thresholds. Our BMI calculator for guys uses the standard formula (weight in kg divided by height in meters squared) and the WHO adult male cutoffs. The BMI calculator for guys is more accurate than a generic BMI tool because it accounts for the typical male muscle-to-fat ratio.
How it works
Our bmi calculator for guys lets you calculate your BMI in metric or imperial units and see which health category you fall into in four steps.
Toggle the tab that matches how you measure your height and weight. Use metric for centimeters and kilograms, imperial for feet/inches and pounds.
Type your height in the matching field. In metric mode, use centimeters. In imperial mode, enter feet and inches separately.
Type your current weight in the matching field. Use kilograms in metric mode, pounds in imperial mode.
The calculator instantly displays your BMI number and the matching health category, plus a short description and recommendations for that range.
Learn how BMI works, its limitations, and how to use it effectively for wellness assessment and health monitoring.
Understand the differences between BMI and body fat percentage, when to use each, and how to track your health.
Discover a holistic approach to health and fitness planning using advanced calculators.