BMI Calculator
This BMI calculator finds your body mass index from your height and weight, in metric or imperial units. You'll get your BMI number, the weight category it falls in, and the healthy weight range for your height, shown on a live gauge. It's a quick way to see where you stand, and it works the same whether you measure in pounds and feet or kilograms and centimetres.
- Metric or imperial
- Weight category
- Healthy weight range
- Live BMI gauge
- WHO bands
Last updated June 16, 2026 Estimates only, not medical advice Reviewed by the Calcowa team
Enter a height and weight above 0.
For adults 20 and over. This is a screening estimate, not medical advice.
703 × 160 ÷ 70² = 23.0
BMI is a screening estimate and not a diagnosis. It doesn't measure body fat directly. Talk to a doctor about your health.
What is BMI?
BMI, or body mass index, is a single number that compares your weight to your height. It's the most common screening tool for weight, used by doctors and health agencies worldwide, because it needs nothing more than a scale and a tape measure. A BMI in the healthy range suggests your weight is reasonable for your height, while a high or low number is a prompt to look closer. It doesn't measure body fat directly, so it's a starting point, not the whole story.
How do you calculate BMI?
Here's the method, for someone 5 feet 10 inches (70 inches) tall weighing 160 pounds:
- 1
Square the heightIn inches: 70 × 70 = 4900. In metric you square the height in metres instead.
- 2
Divide weight by itFor imperial, multiply by 703 first: 703 × 160 = 112,480, then divide by 4900.
- 3
Read the BMIThat gives 23.0, which sits in the healthy-weight band.
- 4
Check the categoryCompare it to the bands: 18.5 to 24.9 is healthy, so 23.0 is right in range.
BMI categories for adults
These are the standard World Health Organization bands for adults. They're the same for men and women.
| BMI | Category |
|---|---|
| Under 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obesity |
Healthy weight range for your height
Here's the weight range that keeps an adult's BMI in the healthy 18.5 to 24.9 band, by height. It's a range rather than one number, because a healthy weight isn't a single point. The calculator above gives the exact range for your own height, but this chart is handy for a quick look.
| Height | Healthy weight (lb) | Healthy weight (kg) |
|---|---|---|
| 5 ft 0 in (152 cm) | 95 to 127 lb | 43 to 58 kg |
| 5 ft 2 in (157 cm) | 101 to 136 lb | 46 to 62 kg |
| 5 ft 4 in (163 cm) | 108 to 145 lb | 49 to 66 kg |
| 5 ft 6 in (168 cm) | 115 to 154 lb | 52 to 70 kg |
| 5 ft 8 in (173 cm) | 122 to 164 lb | 55 to 74 kg |
| 5 ft 10 in (178 cm) | 129 to 174 lb | 59 to 79 kg |
| 6 ft 0 in (183 cm) | 137 to 184 lb | 62 to 84 kg |
| 6 ft 2 in (188 cm) | 144 to 194 lb | 66 to 88 kg |
To plan a change from here, the calorie calculator sets a daily target, and the ideal weight calculator compares the classic formulas side by side.
BMI prime and waist-to-height
BMI prime is a quick twist on the number: it's your BMI divided by 25, the top of the healthy band. A result under 1 means you're within a healthy weight, and a 1.2 says you're about 20% over the upper limit. It's a fast way to see how far you sit from the line without memorizing the bands. For a BMI of 22, the prime is 22 ÷ 25 = 0.88.
Since BMI can't see where fat sits, a useful companion is the waist-to-height ratio: your waist measurement divided by your height, in the same units. Keeping it under 0.5, so your waist is less than half your height, is the common rule of thumb, and it flags the belly fat that BMI misses. Measured together, they give a fuller read than either alone, which is why doctors increasingly look at both.
BMI for men, women, and different ages
The formula and the adult bands don't change with sex or age, so a man and a woman with the same height and weight get the same BMI. What differs is what's underneath it. Women carry more body fat than men on average at the same BMI, and older adults often have less muscle, so an identical number can mean different things from one person to the next. That's a feature of any single screening figure, not a flaw unique to BMI.
Children and teens are the real exception. They don't use the fixed 18.5-to-24.9 bands; instead their BMI is compared to age-and-sex percentile charts, since healthy ranges shift as kids grow. If you're checking a child's BMI, use a pediatric percentile chart rather than the adult result here. For a closer look at fat versus muscle on adults, the body fat calculator uses tape measurements instead.
What BMI doesn't tell you
BMI is quick and handy, but it has real blind spots. It can't tell muscle from fat, so athletes and very muscular people often read as overweight while carrying little fat. It can also understate fat in older adults who've lost muscle, and it wasn't built for children, who use age-and-sex percentiles instead. Pregnancy changes the picture too. So treat your number as a screening flag rather than a verdict, and pair it with how you feel, your waist measurement, and a doctor's input. To turn a body-fat reading or a goal into a percent, the percentage calculator can help, and you'll find more tools on the health and fitness hub.
Frequently asked questions
What's a normal BMI?
A BMI from 18.5 to 24.9 is considered the healthy or normal range for adults. It's the band linked with the lowest health risk on average, though a healthy weight looks a little different for everyone.
BMI is your weight divided by your height squared. In metric that's kilograms ÷ metres², so 70 kg at 1.78 m is 70 ÷ 3.17 = 22.1. In imperial units it's 703 × pounds ÷ inches², so 160 lb at 70 inches is 703 × 160 ÷ 4900 = 23.0. This BMI calculator does the conversion and the math for you in either unit.
For most adults a BMI from 18.5 to 24.9 is the healthy-weight range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more falls into obesity. These bands come from the World Health Organization and apply to adults of any height, since BMI already adjusts for height. The result above shows your band and your healthy weight range.
BMI is a useful screening number, not a diagnosis. It doesn't tell muscle from fat, so a very muscular person can read high while still being lean, and it can understate fat in older adults who've lost muscle. It also wasn't designed for children, pregnancy, or athletes. Treat it as a quick flag, and talk to a doctor for a fuller picture.
Your healthy weight range is whatever puts your BMI between 18.5 and 24.9 for your height. The calculator works it out and shows the low and high ends in your chosen unit. For someone 5 feet 10 inches tall, that's roughly 129 to 174 pounds. It's a range, not a single number, because healthy weight varies from person to person.
The BMI formula and the adult categories are the same for men and women, so the number is figured the same way. Body composition does differ on average, with women usually carrying more body fat at the same BMI, which is one reason BMI is a rough guide rather than a precise measure of fat. For body fat specifically, a dedicated method works better.
Squaring the height keeps the number roughly comparable across people of different heights, so a tall and a short person at a healthy weight land in the same band. It isn't perfect, since very tall people skew a little high, but it's simple, needs only a scale and a tape measure, and it's been the standard screening tool for decades.
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