How to use this calculator
Choose US or metric units, then enter your height and weight. Your BMI updates as you type, along with:
- your BMI category on the adult scale
- the healthy weight range for your height (BMI 18.5 to 24.9)
- how much you’d need to gain or lose to reach that range
- the calculation itself, step by step
The BMI formula
BMI divides weight by the square of height:
In US units the same calculation uses a conversion factor of 703:
Example: someone 5 ft 9 in (69 inches) tall weighing 160 lb has a BMI of 703 × 160 ÷ 69² = 112,480 ÷ 4,761 ≈ 23.6, which is in the healthy range. For that height, the healthy range runs from about 125 to 169 lb.
Adult BMI categories
| 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 |
| 40.0 and above | Obesity, class 3 (severe) |
These ranges, used by the CDC and WHO, apply to adults 20 and older regardless of sex. Some health bodies use lower cutoffs for people of Asian descent, because health risks tend to rise at a lower BMI.
Healthy weight by height
This chart shows the weight ranges for each BMI category at common adult heights. Weights are rounded to the nearest pound. For heights in between, use the calculator above for an exact answer.
| Height | Healthy (18.5–24.9) | Overweight (25–29.9) | Obesity (30+) |
|---|---|---|---|
| 4 ft 10 in | 89 – 119 lb | 120 – 143 lb | 144 lb or more |
| 5 ft 0 in | 95 – 128 lb | 129 – 153 lb | 154 lb or more |
| 5 ft 2 in | 101 – 136 lb | 137 – 163 lb | 164 lb or more |
| 5 ft 4 in | 108 – 145 lb | 146 – 174 lb | 175 lb or more |
| 5 ft 6 in | 115 – 154 lb | 155 – 185 lb | 186 lb or more |
| 5 ft 8 in | 122 – 164 lb | 165 – 197 lb | 198 lb or more |
| 5 ft 10 in | 129 – 174 lb | 175 – 208 lb | 209 lb or more |
| 6 ft 0 in | 136 – 184 lb | 185 – 220 lb | 221 lb or more |
| 6 ft 2 in | 144 – 194 lb | 195 – 233 lb | 234 lb or more |
| 6 ft 4 in | 152 – 205 lb | 206 – 246 lb | 247 lb or more |
The same principle works in reverse: a weight that sits in the middle of the healthy range for a shorter person can be underweight for someone taller. That is why BMI uses height squared rather than weight alone.
What BMI can and can’t tell you
BMI became the standard screening tool because it only needs a scale and a tape measure, and at a population level a higher BMI is linked to a higher risk of type 2 diabetes, heart disease and high blood pressure. But it has real limits for any one person:
- It doesn’t measure body fat directly. Muscle is denser than fat, so strength athletes often score as “overweight” while being lean.
- It ignores where fat sits. Fat around the abdomen carries more health risk than fat elsewhere. A waist measurement over 40 inches (102 cm) for men or 35 inches (88 cm) for women is a separate warning sign.
- It shifts with age. Older adults lose muscle, so a “healthy” BMI can hide low muscle and high fat.
Treat your BMI as a starting point for a conversation with your doctor, not a verdict. Pair it with waist circumference, blood pressure, blood sugar and cholesterol for a fuller picture.
If you’d like to change your BMI
Small, sustainable changes work best. Most guidelines suggest aiming for 1 to 2 pounds (0.5 to 1 kg) of weight loss a week. Our calorie calculator and TDEE calculator can help you set a daily calorie target. Building muscle through strength training can improve your health even when your BMI barely moves.
This calculator is for adults and is for general information only. It isn’t medical advice.
Frequently asked questions
What is a healthy BMI?
For adults 20 and older, a BMI from 18.5 to 24.9 is classed as healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or higher is obesity. These are the categories used by the CDC and the World Health Organization.
How do you calculate BMI?
BMI is your weight in kilograms divided by your height in meters squared. In US units, multiply your weight in pounds by 703 and divide by your height in inches squared. For example, 160 lb at 5 ft 9 in (69 inches) is 703 × 160 ÷ 4,761 ≈ 23.6.
Is BMI accurate?
BMI is a quick, inexpensive screening measure that correlates with body fat at the population level, but it can't tell muscle from fat or show where fat is stored. Muscular athletes can have a high BMI without excess fat, and older adults can have a normal BMI with low muscle mass. Waist size and other measurements give a fuller picture.
Is BMI different for men and women?
For adults, the same BMI categories apply to men and women. Women naturally tend to carry more body fat than men at the same BMI, which is one reason a doctor may consider other measures alongside it.
Can I use this BMI calculator for children?
No. For children and teens aged 2 to 19, BMI is interpreted using age- and sex-specific growth charts that give a percentile. The adult categories on this page don't apply to them.
What is BMI Prime?
BMI Prime is your BMI divided by 25, the upper limit of the healthy range. A value under 1.0 means you're below that limit; 1.2 means your BMI is 20% above it. It makes it easy to see how far you are from the cutoff.
Updated November 2026. Results are estimates for educational purposes and depend on the inputs you provide.