How to calculate BMI (formula and example)
Body mass index (BMI) compares your weight to your height. It was designed to screen large groups of people quickly, and it's still the first number most clinicians look at when they talk about weight and health.
The formula is older than most people expect. The Belgian mathematician Adolphe Quetelet devised it in the 1830s, and the physiologist Ancel Keys named it "body mass index" in 1972, after comparing it with other height and weight measures.
This calculator uses the same formula and rounding as the CDC's adult BMI calculator:
BMI = weight (lb) ÷ height (in)² × 703
A worked example
Someone who is 5 ft 6 in (66 inches) and weighs 190 lb has a BMI of 190 ÷ (66 × 66) × 703 = 30.7. That falls in the class 1 obesity range. The healthy range for that height is roughly 115 to 154 lb.
BMI chart for adults: ranges and categories
On the adult BMI chart, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or higher is obesity, split into three classes. Below 18.5 is underweight. The cut-offs are the same for all adults, whatever their age or sex:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity, class 1 |
| 35.0 – 39.9 | Obesity, class 2 |
| 40 and above | Obesity, class 3 |
Class 3 obesity (a BMI of 40 or higher) is sometimes called severe obesity; older sources call it morbid obesity.
Full BMI chart
To read the chart, find your height on the left and the weight closest to yours across the top, in pounds. Each cell is the BMI for that height and weight, rounded the same way as the calculator, and shaded by category. For your exact number, use the calculator above.
- Underweight (Below 18.5)
- Healthy weight (18.5 – 24.9)
- Overweight (25.0 – 29.9)
- Obesity, class 1 (30.0 – 34.9)
- Obesity, class 2 (35.0 – 39.9)
- Obesity, class 3 (40 and above)
| Height | 100 lb | 120 lb | 140 lb | 160 lb | 180 lb | 200 lb | 220 lb | 240 lb | 260 lb | 280 lb | 300 lb |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 4'10" | 20.9 | 25.1 | 29.3 | 33.4 | 37.6 | 41.8 | 46.0 | 50.2 | 54.3 | 58.5 | 62.7 |
| 5'0" | 19.5 | 23.4 | 27.3 | 31.2 | 35.2 | 39.1 | 43.0 | 46.9 | 50.8 | 54.7 | 58.6 |
| 5'2" | 18.3 | 21.9 | 25.6 | 29.3 | 32.9 | 36.6 | 40.2 | 43.9 | 47.5 | 51.2 | 54.9 |
| 5'4" | 17.2 | 20.6 | 24.0 | 27.5 | 30.9 | 34.3 | 37.8 | 41.2 | 44.6 | 48.1 | 51.5 |
| 5'6" | 16.1 | 19.4 | 22.6 | 25.8 | 29.0 | 32.3 | 35.5 | 38.7 | 42.0 | 45.2 | 48.4 |
| 5'8" | 15.2 | 18.2 | 21.3 | 24.3 | 27.4 | 30.4 | 33.4 | 36.5 | 39.5 | 42.6 | 45.6 |
| 5'10" | 14.3 | 17.2 | 20.1 | 23.0 | 25.8 | 28.7 | 31.6 | 34.4 | 37.3 | 40.2 | 43.0 |
| 6'0" | 13.6 | 16.3 | 19.0 | 21.7 | 24.4 | 27.1 | 29.8 | 32.5 | 35.3 | 38.0 | 40.7 |
| 6'2" | 12.8 | 15.4 | 18.0 | 20.5 | 23.1 | 25.7 | 28.2 | 30.8 | 33.4 | 35.9 | 38.5 |
| 6'4" | 12.2 | 14.6 | 17.0 | 19.5 | 21.9 | 24.3 | 26.8 | 29.2 | 31.6 | 34.1 | 36.5 |
Is BMI different for women and men?
No. Adult women and men use the same BMI formula and the same categories, so a BMI of 25 is overweight and 30 is obesity for both. What differs is what the number hides: at the same BMI, women tend to carry more body fat than men, and men tend to carry more muscle.
That's why a BMI calculator for women and a BMI calculator for men give the same answer for the same height and weight. Sex isn't part of the formula, and the healthy weight range for a given height is the same too.
Where sex does come in is waist size, a simple check on the fat BMI can't see. Guidelines from the National Heart, Lung, and Blood Institute (NHLBI) link a waist of more than 35 inches for women or more than 40 inches for men with a higher risk of type 2 diabetes, high blood pressure and heart disease. To measure, wrap a tape around your bare waist just above your hip bones, and read it after you breathe out.
Does BMI change with age?
Not for adults. From age 20 on, the BMI formula and the categories stay the same, so a BMI of 25 to 29.9 is overweight whether you're 25, 45 or 75 years old. Under 20 it works differently: children and teens are compared with others of the same age and sex, using BMI-for-age percentiles instead of fixed cut-offs.
What does change with age is body composition. Muscle tends to decline over the years, so at the same BMI, older adults on average carry more body fat than younger adults.
Healthy weight for your height (women and men)
A healthy weight for your height is any weight that gives you a BMI of 18.5 to 24.9. At 5 ft 4 in, that's about 108 to 145 lb, and at 5 ft 10 in, about 129 to 173 lb. The ranges are the same for women and men, because the formula doesn't change with sex.
Here's the healthy range for every inch from 4 ft 10 in to 6 ft 6 in, calculated the same way as the tool above. It also shows the weight where overweight (BMI 25) and obesity (BMI 30) start at each height.
| Height | Healthy weight (lb) | Overweight from (BMI 25) | BMI 30 starts at |
|---|---|---|---|
| 4 ft 10 in | 89–119 | 120 lb | 144 lb |
| 4 ft 11 in | 92–123 | 124 lb | 149 lb |
| 5 ft 0 in | 95–127 | 128 lb | 154 lb |
| 5 ft 1 in | 98–132 | 133 lb | 159 lb |
| 5 ft 2 in | 101–136 | 137 lb | 164 lb |
| 5 ft 3 in | 105–140 | 141 lb | 170 lb |
| 5 ft 4 in | 108–145 | 146 lb | 175 lb |
| 5 ft 5 in | 111–149 | 150 lb | 180 lb |
| 5 ft 6 in | 115–154 | 155 lb | 186 lb |
| 5 ft 7 in | 118–159 | 160 lb | 192 lb |
| 5 ft 8 in | 122–164 | 165 lb | 197 lb |
| 5 ft 9 in | 125–168 | 169 lb | 203 lb |
| 5 ft 10 in | 129–173 | 174 lb | 209 lb |
| 5 ft 11 in | 133–178 | 179 lb | 215 lb |
| 6 ft 0 in | 137–183 | 184 lb | 221 lb |
| 6 ft 1 in | 140–189 | 190 lb | 228 lb |
| 6 ft 2 in | 144–194 | 195 lb | 234 lb |
| 6 ft 3 in | 148–199 | 200 lb | 240 lb |
| 6 ft 4 in | 152–204 | 205 lb | 247 lb |
| 6 ft 5 in | 156–210 | 211 lb | 253 lb |
| 6 ft 6 in | 160–215 | 216 lb | 260 lb |
Whole pounds, rounded the way the CDC does.
What BMI range are GLP-1 medications prescribed for?
For chronic weight management, the FDA-approved labels of brand-name semaglutide and tirzepatide (Wegovy® and Zepbound®) cover adults with a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related condition. BMI is where that guidance starts; a licensed clinician makes the decision. New to these medications? Here's how GLP-1 medications work, in plain terms.
BMI of 30 or higher
A BMI of 30 or higher is classed as obesity, and on the brand-name labels it's within the range on its own, with or without another health condition. At 5 ft 4 in, a BMI of 30 starts at about 175 lb; at 5 ft 10 in, at about 209 lb. The healthy weight chart by height shows where it starts for every height.
BMI of 27 to 29.9 with a weight-related condition
Between 27 and 29.9, the labels add a condition: at least one weight-related health problem, such as high blood pressure, high cholesterol, type 2 diabetes, obstructive sleep apnea or heart disease. At 5 ft 4 in, a BMI of 27 starts at about 158 lb; at 5 ft 10 in, at about 188 lb.
BMI of 25 to 26.9
Some adults with a BMI of 25 or higher are still candidates, depending on their medical history, current medications and goals.
For a longer walk-through of how BMI and your health history fit together, read our guide to GLP-1 eligibility.
Your next step
See if GLP-1 treatment is right for you
Answer a few questions about your health, medications and goals. A licensed clinician reviews your intake and decides whether treatment is right for you.
- Typically reviewed within 24 hours
- Only charged if prescribed
- No insurance required
Compounded medications prescribed through Yucca Health are not FDA-approved.
Is BMI accurate? What it can't tell you
BMI is useful because it's simple. The trade-off is that it leaves a lot out:
- Muscle versus fat. Muscle is denser than fat, so athletes and very muscular people can land in the overweight range with little body fat.
- Where fat is stored. Fat around the waist carries more health risk than fat elsewhere. A waist measurement adds information BMI can't (see the waist sizes for women and men).
- Age. Body composition changes with age.
A simple companion measure is your waist-to-height ratio: your waist circumference divided by your height, in the same units. Guidance from the UK's National Institute for Health and Care Excellence (NICE) suggests keeping it under 0.5.
What does a BMI of 25, 27 or 30 mean? Quick answers
A BMI of 25 is where the overweight range starts, 27 sits inside it, and 30 is where obesity starts on the adult chart. Here are short answers to the BMI questions people ask most, with the math shown.
- Is a BMI of 25 good? A BMI of 25.0 is the first number in the overweight range; the healthy range ends at 24.9.
- Is a BMI of 27 overweight? Yes. 27 is in the overweight range (25 to 29.9). It's also the BMI that brand-name GLP-1 labels pair with a weight-related condition, as explained above.
- Is a BMI of 30 obese? Yes. For adults, a BMI of 30.0 or higher is classed as obesity: 30 to 34.9 is class 1, 35 to 39.9 is class 2, and 40 or higher is class 3.
- What weight is a BMI of 30 at 5 ft 4 in? About 175 lb. At 64 inches, 30 × 64 × 64 ÷ 703 = 174.8 lb, and 175 lb is the first whole pound that rounds to a BMI of 30.0. The table by height shows it for every height from 4 ft 10 in to 6 ft 6 in.
- How much weight do I need to lose to get my BMI under 30? Work out the weight at a BMI of 29.9 for your height: 29.9 × your height in inches × your height in inches ÷ 703. The difference between that and your current weight is the answer. At 5 ft 6 in and 190 lb, for example, a BMI under 30 means 185 lb or less, so about 5 lb. The calculator above does the same math for a BMI under 25, the top of the healthy range.
What to do with your BMI calculator result
- In the healthy range: keep up the habits that got you there: enough protein, water, sleep and movement.
- Overweight or higher: small, steady changes add up, and for some people medication is part of the plan. Start with the TDEE calculator: your maintenance calories are the number every eating plan is built from.
- If you're losing weight: enough protein and regular strength training help you keep muscle while the number comes down. If you're on a GLP-1, here's a beginner's strength-training plan.
Sources
7 references
- Centers for Disease Control and Prevention. Adult BMI categories and BMI frequently asked questions.
- National Heart, Lung, and Blood Institute. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults: the evidence report. NIH Publication No. 98-4083, 1998.
- Gallagher D, et al. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. American Journal of Clinical Nutrition. 2000;72:694–701.
- Keys A, et al. Indices of relative weight and obesity. Journal of Chronic Diseases. 1972;25:329–343.
- Eknoyan G. Adolphe Quetelet (1796–1874): the average man and indices of obesity. Nephrology Dialysis Transplantation. 2008;23:47–51.
- U.S. Food and Drug Administration. Prescribing information for Wegovy® (semaglutide) injection, 2021 and 2026, and Zepbound® (tirzepatide) injection, 2023 and 2026. Drugs@FDA.
- National Institute for Health and Care Excellence. Overweight and obesity management (NG246), 2025.
Licensed providers.
