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BMI is your weight in kilograms divided by your height in meters squared. A 5'10" person weighing 180 lbs has a BMI of 25.8 — just into the "overweight" range. Enter your height and weight to calculate yours instantly.
Body Mass Index has been used for nearly 200 years as a quick way to categorize weight relative to height. It is not a perfect measure — and we will be honest about exactly where it falls short — but it remains the most widely used screening tool in medicine because it is fast, free, and requires nothing but a scale and a tape measure.
BMI measures one thing: the ratio of your weight to your height. That is it. It does not measure body fat, muscle mass, bone density, water retention, or fitness level. It cannot tell you where your fat is stored, whether your cholesterol is high, or whether you exercise five days a week.
What it does do is provide a quick, standardized number that correlates — at the population level — with certain health outcomes. People with BMIs over 30 are, on average, at higher risk for type 2 diabetes, heart disease, and certain cancers. People with BMIs under 18.5 are at higher risk for nutritional deficiencies, osteoporosis, and immune system problems.
The key phrase is "on average." BMI works as a statistical tool across large populations. It falls apart when applied to individuals who do not fit the average body type — athletes, elderly people, and people of certain ethnic backgrounds.
The formula is simple. In metric units:
BMI = weight (kg) / height (m)²
In imperial units:
BMI = (weight (lbs) x 703) / height (inches)²
The 703 multiplier converts from the imperial measurement to match the metric-based scale. The formula was created by Adolphe Quetelet, a Belgian mathematician, in the 1830s. He was studying population statistics, not individual health. The term "Body Mass Index" was not coined until 1972 by researcher Ancel Keys, who argued it was the best simple proxy for body fat in population studies.
| Category | BMI Range | Health Risk Context |
|---|---|---|
| Underweight | Below 18.5 | Higher risk of nutritional deficiencies, osteoporosis, weakened immune system |
| Normal weight | 18.5 – 24.9 | Lowest statistical risk for weight-related health problems |
| Overweight | 25.0 – 29.9 | Moderately increased risk of heart disease, type 2 diabetes, high blood pressure |
| Obese Class I | 30.0 – 34.9 | High risk of metabolic syndrome, sleep apnea, joint problems |
| Obese Class II | 35.0 – 39.9 | Very high risk of serious health complications |
| Obese Class III | 40.0+ | Highest risk category; significant impact on life expectancy and quality of life |
Find your height in the left column, then trace across to see what different weights mean for your BMI. The color thresholds: under 18.5 is underweight, 18.5-24.9 is normal, 25-29.9 is overweight, and 30+ is obese.
| Height | 120 lbs | 140 lbs | 160 lbs | 180 lbs | 200 lbs | 220 lbs | 240 lbs | 260 lbs | 280 lbs | 300 lbs |
|---|---|---|---|---|---|---|---|---|---|---|
| 5'0" | 23.4 | 27.3 | 31.2 | 35.2 | 39.1 | 43.0 | 46.9 | 50.8 | 54.7 | 58.6 |
| 5'2" | 21.9 | 25.6 | 29.3 | 32.9 | 36.6 | 40.2 | 43.9 | 47.6 | 51.2 | 54.9 |
| 5'4" | 20.6 | 24.0 | 27.5 | 30.9 | 34.3 | 37.8 | 41.2 | 44.6 | 48.1 | 51.5 |
| 5'6" | 19.4 | 22.6 | 25.8 | 29.1 | 32.3 | 35.5 | 38.7 | 42.0 | 45.2 | 48.4 |
| 5'8" | 18.2 | 21.3 | 24.3 | 27.4 | 30.4 | 33.5 | 36.5 | 39.5 | 42.6 | 45.6 |
| 5'10" | 17.2 | 20.1 | 23.0 | 25.8 | 28.7 | 31.6 | 34.4 | 37.3 | 40.2 | 43.0 |
| 6'0" | 16.3 | 19.0 | 21.7 | 24.4 | 27.1 | 29.8 | 32.6 | 35.3 | 38.0 | 40.7 |
| 6'2" | 15.4 | 18.0 | 20.5 | 23.1 | 25.7 | 28.2 | 30.8 | 33.4 | 35.9 | 38.5 |
| 6'4" | 14.6 | 17.0 | 19.5 | 21.9 | 24.3 | 26.8 | 29.2 | 31.6 | 34.1 | 36.5 |
| Feature | WildandFree BMI Calculator | CDC BMI Calculator | NHS BMI Checker | Mayo Clinic | WebMD |
|---|---|---|---|---|---|
| Free | ✓ Completely free | ✓ Free | ✓ Free | ✓ Free | ✓ Free |
| No signup required | ✓ No account needed | ✓ No signup | ✓ No signup | ✓ No signup | ✗ Asks for account |
| Shows BMI category | ✓ Instant category | ✓ Shows category | ✓ Shows category | ~General guidance | ✓ Shows category |
| Shows healthy weight range | ✓ Full range displayed | ~Limited context | ✓ Shows range | ~General advice | ~Limited |
| Supports metric + imperial | ✓ Both units | ✓ Both units | ~Metric default | ✓ Both units | ✓ Both units |
| Mobile friendly | ✓ Fully responsive | ~Functional | ✓ Responsive | ✓ Responsive | ~Ad-heavy on mobile |
| No ads | ✓ Zero ads | ✓ No ads | ✓ No ads | ~Minimal ads | ✗ Heavy ad load |
| Instant results | ✓ Client-side, instant | ✓ Fast | ✓ Fast | ✓ Fast | ~Slower with ads |
Doctors know BMI is imperfect. Researchers have published thousands of papers documenting its limitations. So why does every doctor's office still calculate it?
Three reasons. First, it is universal — every adult on earth can calculate their BMI with a scale and a measuring tape. No blood draw, no expensive scan, no equipment beyond what you already have at home. Second, it correlates well enough at the population level that public health agencies can use it to track obesity trends and allocate resources. Third, there is no better simple alternative. Body fat percentage is more accurate but requires calipers, DEXA scans, or bioelectrical impedance devices that cost hundreds to thousands of dollars.
BMI is the blood pressure cuff of weight assessment — it is a quick screening tool that tells you whether you need a closer look, not a final diagnosis.
BMI systematically misclassifies several groups of people:
Important: This calculator is a math tool, not medical advice. BMI does not distinguish between muscle and fat. A bodybuilder and an obese person at the same height and weight have the same BMI. It is a screening tool, not a diagnostic one. Always consult a healthcare professional for medical assessments.
Calculate your BMI right now — enter your height and weight for an instant result.
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