BMI Calculator
1Your height and weight
Your body mass index
–
25Obesity I
30Obesity II
35Obesity III
40+
Your BMI, four ways
Your WHO category always comes from the standard BMI. The new BMI corrects the standard formula for very short and very tall adults, BMI Prime expresses your BMI as a share of the top of the healthy range (1.00 = BMI 25), and the ponderal index divides by height cubed. Only the standard BMI has official categories.
WHO adult categories at your height
Next step: BMI cannot tell muscle from fat. Check your body composition with the body fat calculator, then set daily calories with the TDEE calculator.
Open the TDEE calculatorFor general information only, not medical advice. These formulas estimate population averages and can be off for an individual; talk to your doctor or a registered dietitian before changing your diet or training, especially with a health condition, during pregnancy or for anyone under 18.
Free tool · Updated November 3, 2026
One number, four ways to read it
Enter your height and weight in pounds and inches or kilograms and centimeters. The calculator gives your BMI with its WHO category, three alternative indices, and the weight range that counts as healthy for your height.
Short answer
Body mass index is your weight in kilograms divided by your height in meters squared, or 703 times pounds divided by inches squared. For example, a 5 ft 9 in adult who weighs 180 lb has a BMI of 26.6, in the overweight range; the healthy range at that height is about 126 to 168 lb. Enter your own numbers below to see your BMI, the new BMI, BMI Prime and the ponderal index.
Key takeaways
- A BMI from 18.5 to 24.9 is the healthy range for adults, the same for men and women.
- The calculator turns that range into pounds and kilograms for your height.
- BMI cannot tell muscle from fat: athletes and strength-trained people often read as overweight.
- For children and teens, BMI is read on age and sex growth charts, not on the adult categories.
A BMI calculator is the quickest screening tool for body weight: one division, a number and a category. Doctors, insurers and public health agencies use it because it needs only a scale and a tape measure, and because it tracks health risks well across large groups of people.
The same simplicity is its limit. BMI does not know whether your weight is muscle or fat, where the fat sits, or how your age and ancestry change the picture. This page gives you the standard BMI with its official categories, three alternative indices that correct some of its quirks, and a clear account of what the number can and cannot tell you.
How to Calculate BMI
Divide your weight in kilograms by your height in meters, then divide again by your height (that is, by height squared). In US units, multiply your weight in pounds by 703 and divide by your height in inches squared. Both give the same number; the calculator accepts either and shows results in both.
BMI uses the same formula and the same categories for men and women. A BMI calculator for women gives exactly the same result as one for men; what differs is body composition, since women carry more body fat than men at the same BMI on average.
| Index | Formula | Example: 5 ft 9 in, 180 lbExample |
|---|---|---|
| Standard BMI (metric) | W in kg / (H in m)² | 81.6 kg / 1.753² = 26.6 |
| Standard BMI (US) | 703 x W in lb / (H in in)² | 703 x 180 / 69² = 26.6 |
| New BMI (Trefethen) | 1.3 x W in kg / (H in m)^2.5 | 26.1 |
| BMI Prime | BMI / 25 | 1.06 |
| Ponderal index | W in kg / (H in m)³ | 15.2 |
BMI Categories for Adults
The World Health Organization and the National Heart, Lung, and Blood Institute use the same cut-offs for adults aged 20 and over. The BMI Prime column divides each cut-off by 25, the top of the healthy range.
| BMI | WHO category | BMI Prime |
|---|---|---|
| Below 18.5 | Underweight | below 0.74 |
| 18.5 to 24.9 | Healthy weight (normal range) | 0.74 to 1.00 |
| 25 to 29.9 | Overweight (pre-obesity) | 1.00 to 1.20 |
| 30 to 34.9 | Obesity, class 1 | 1.20 to 1.40 |
| 35 to 39.9 | Obesity, class 2 | 1.40 to 1.60 |
| 40 and above | Obesity, class 3 | 1.60 and above |
Healthy Weight Range by Height
A healthy BMI from 18.5 to 24.9 covers a wide band of weights at any height, about 40 lb for an average adult. Where you sit inside it depends on your frame and your muscle. The table gives the range for common heights; the calculator works it out for your exact height.
| Height | Healthy weight (lb)Pounds | Healthy weight (kg)Kilograms | Top of overweight (BMI 29.9)BMI 29.9 |
|---|---|---|---|
| 4 ft 10 in (147 cm) | 89 to 119 lb | 40 to 54 kg | 143 lb |
| 5 ft 0 in (152 cm) | 95 to 127 lb | 43 to 58 kg | 153 lb |
| 5 ft 2 in (157 cm) | 102 to 136 lb | 46 to 62 kg | 163 lb |
| 5 ft 4 in (163 cm) | 108 to 145 lb | 49 to 66 kg | 174 lb |
| 5 ft 6 in (168 cm) | 115 to 154 lb | 52 to 70 kg | 185 lb |
| 5 ft 8 in (173 cm) | 122 to 163 lb | 55 to 74 kg | 196 lb |
| 5 ft 10 in (178 cm) | 129 to 173 lb | 59 to 78 kg | 208 lb |
| 6 ft 0 in (183 cm) | 137 to 183 lb | 62 to 83 kg | 220 lb |
| 6 ft 2 in (188 cm) | 145 to 193 lb | 66 to 88 kg | 232 lb |
| 6 ft 4 in (193 cm) | 152 to 204 lb | 69 to 93 kg | 245 lb |
New BMI, BMI Prime and the Ponderal Index
The standard BMI divides by height squared, but bodies do not scale that way: tall people come out with a higher BMI than their build suggests, and short people with a lower one. Oxford mathematician Nick Trefethen proposed a new BMI of 1.3 x weight / height^2.5, scaled so that it matches the standard BMI for a person of average height.
BMI Prime is your BMI divided by 25. It makes the distance to the top of the healthy range obvious: 1.10 means 10% above it. The ponderal index (also called the Rohrer index) divides weight by height cubed, which removes most of the height effect; it is used mostly for newborns and in research, and has no official adult categories.
What BMI Cannot Tell You
- Muscle or fat. Two people with the same BMI can have very different body fat. Athletes and people who lift often read as overweight while being lean; the body fat calculator measures body composition instead.
- Where the fat sits. Fat around the waist carries more health risk than fat on the hips and thighs. Waist size adds what BMI misses.
- Age. Older adults tend to lose muscle and gain fat at the same weight, so a normal BMI can hide a higher body fat. The adult categories also do not apply under age 20.
- Ancestry. At the same BMI, people of Asian descent tend to carry more body fat than people of European descent. A WHO expert consultation in The Lancet (2004) proposed extra public health action points at a BMI of 23 and 27.5 for Asian populations.
- Pregnancy. BMI is not meaningful during pregnancy; weight gain targets are based on the BMI before pregnancy.
From Your BMI to a Plan
- Pick a target. The ideal body weight calculator compares eight target-weight formulas with your healthy BMI range and your frame size.
- Find your calories. The TDEE calculator turns your weight, height, age and activity into a daily calorie target for slow, steady loss.
- Walk every day. Brisk walking, especially on an incline, adds steady calorie burn; the treadmill calorie calculator shows how much for your pace.
- Make it easy at home. A treadmill removes weather and commute from the plan; compare our best treadmills for weight loss.
Share, Embed or Cite This Calculator
You are welcome to link to this BMI calculator. The result link keeps your inputs; the embed code adds the calculator to your page with a visible credit link.
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Cite this calculator
- TitleBMI Calculator
- PublisherFitGearHQ
- URLhttps://fitgearhq.com/bmi-calculator/
- Updated
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Checklist Before You Calculate Your BMI
4 checks
Tap a number to check off that step.
- 01
Measure height without shoesStand straight against a wall, heels together, and mark the top of your head.
- 02
Weigh in the morningSame scale, after the bathroom and before breakfast, in light clothing.
- 03
Use exact numbersHalf an inch or a pound or two moves BMI by a few tenths.
- 04
Read it with your waistA tape around the waist adds what BMI cannot see.
Common Mistakes to Avoid
Mistake 1Reading BMI as body fat
Instead: BMI estimates weight for height, not fat; muscular people read high.
Mistake 2Using adult categories for teens
Instead: Under age 20, BMI is read on age and sex growth charts.
Mistake 3Chasing the bottom of the range
Instead: Anywhere from 18.5 to 24.9 is healthy; there is no single ideal number.
Mistake 4Checking every day
Instead: Water and food move your weight; track the weekly average instead.
The Bottom Line
- Standard BMI (US and metric), new BMI (Trefethen), BMI Prime and ponderal index.
- The six WHO adult categories, with your weight range in each.
- Healthy weight range and the change needed to reach it.
- US and metric units; the link keeps your inputs.
Frequently Asked Questions
For adults aged 20 and over, a BMI from 18.5 to 24.9 is the healthy range used by the WHO and the NHLBI. Below 18.5 is underweight, 25 to 29.9 overweight and 30 or more obesity.
No. Adult BMI uses the same formula and the same categories for women and men. Women carry more body fat than men at the same BMI on average, which is why a body fat estimate is a useful second check.
Multiply your weight in pounds by 703, then divide by your height in inches squared. For 180 lb at 69 inches: 703 x 180 / 4,761 = 26.6.
A formula proposed by Nick Trefethen of Oxford University: 1.3 x weight in kg / height in m to the power 2.5. It gives tall people a slightly lower value and short people a slightly higher one than the standard BMI.
Your BMI divided by 25, the upper limit of the healthy range. A BMI Prime from 0.74 to 1.00 is the healthy range; 1.20 means your BMI is 20% above it.
Not very. Muscle is dense, so muscular people often have a BMI in the overweight range with low body fat. A body fat estimate is more useful for them.
The adult cut-offs are the same at every age from 20. Older adults often have more body fat at the same BMI, so waist size and body fat are worth checking too.
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