BMI Calculator
Calculate your body mass index (BMI) from your height and weight in metric or imperial units. See your adult BMI category and the weight range that matches a BMI of 18.5 to 24.9 for your height.
How to Use the BMI Calculator
- Choose your units: Use the toggle to pick Metric (kilograms and centimetres) or Imperial (pounds, feet and inches).
- Enter your weight: Type your current weight. Weigh yourself at a consistent time of day if you plan to compare results.
- Enter your height: Type centimetres, or feet and inches. In imperial mode you can enter inches alone by leaving feet blank.
- Read your results: Your BMI, adult category and healthy weight range update as you type. Use Clear to start over or Share to send the result.
What You'll Discover
- Your BMI — your weight divided by the square of your height, shown to one decimal place.
- Your category — Underweight, Normal weight, Overweight, or Obese with its class (1, 2 or 3), using the adult thresholds the CDC and WHO publish.
- Healthy weight range — the weights that give a BMI of 18.5 to 24.9 at your height, in the units you chose.
- Your weight vs that range — how many kilograms or pounds you are below or above the range, or "Within range".
BMI is a screening measure, not a diagnosis. This calculator is for information only and is not medical advice. It is meant for adults and does not use age, sex, muscle mass or ethnicity. For personal guidance, talk to a doctor or other health professional. More tools are in our health calculators hub.
How BMI Is Calculated
BMI is your weight divided by your height squared. The CDC defines it as weight in kilograms divided by height in metres squared, and the WHO uses the same formula. Because height is squared, the same weight gives a very different BMI for a short person and a tall one.
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lb) ÷ height (in)²
Worked example in metric units
A person who weighs 70 kg and is 175 cm tall (1.75 m): 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.857. The calculator shows 22.9, which is Normal weight.
Worked example in imperial units
A person who weighs 154 lb and is 5 ft 9 in tall (69 inches): 69 × 69 = 4,761, and 703 × 154 = 108,262, so 108,262 ÷ 4,761 = 22.739. That rounds to 22.7, also Normal weight.
The factor 703 is a rounded form of the pound-to-kilogram and inch-to-metre conversions (the exact figure is about 703.07). The calculator converts your pounds and inches to kilograms and metres first and then applies the metric formula, so a hand calculation with 703 can differ from it by a few thousandths in the examples on this page.
How the result is rounded
BMI is shown to one decimal place, but the category is decided on the unrounded value. At 175 cm, a weight of 76.5 kg gives 24.98, which is still below 25 and so still Normal weight. The calculator shows 24.98 rather than 25.0 in that case, so the number on screen never contradicts the category next to it.
Adult BMI Categories and Healthy Weight by Height
For adults aged 20 and over, the CDC lists these BMI categories. The WHO uses the same cut-offs for overweight (25 or above) and obesity (30 or above).
| BMI | CDC adult category | Label this calculator shows |
|---|---|---|
| Less than 18.5 | Underweight | Underweight |
| 18.5 to less than 25 | Healthy weight | Normal weight |
| 25 to less than 30 | Overweight | Overweight |
| 30 to less than 35 | Class 1 obesity | Obese (Class 1) |
| 35 to less than 40 | Class 2 obesity | Obese (Class 2) |
| 40 or greater | Class 3 obesity (severe obesity) | Obese (Class 3) |
The thresholds do not change with age or sex in this adult table, which is why the calculator does not ask for either. Where your own risk sits depends on much more than the category, so use it as a starting point for a conversation with a clinician.
Healthy weight range by height
The healthy weight range is the set of weights that give a BMI from 18.5 to 24.9 at a given height. These rows are calculated with the same formula as the calculator above.
| Height | Weight for BMI 18.5 to 24.9 (kg) | Weight for BMI 18.5 to 24.9 (lb) |
|---|---|---|
| 5 ft 0 in (152.4 cm) | 43.0 – 57.8 kg | 94.7 – 127.5 lb |
| 5 ft 3 in (160.0 cm) | 47.4 – 63.8 kg | 104.4 – 140.6 lb |
| 5 ft 6 in (167.6 cm) | 52.0 – 70.0 kg | 114.6 – 154.3 lb |
| 5 ft 9 in (175.3 cm) | 56.8 – 76.5 kg | 125.3 – 168.6 lb |
| 6 ft 0 in (182.9 cm) | 61.9 – 83.3 kg | 136.4 – 183.6 lb |
| 6 ft 3 in (190.5 cm) | 67.1 – 90.4 kg | 148.0 – 199.2 lb |
What BMI Cannot Tell You
The CDC describes BMI as a quick, inexpensive screening measure, and says it does not directly measure body fat. It is, however, moderately to strongly associated with other measures of body fat. Its limits matter when you read your own number.
- Fat, muscle and bone look the same. The CDC notes that BMI does not distinguish between fat, muscle and bone mass, all of which add to your weight. A very muscular person can have a high BMI without carrying much fat.
- It does not show where fat is carried. The CDC also notes that BMI does not indicate what types of fat a person has or where in the body they carry it.
- Children and teens use percentiles. The CDC compares a child's BMI with other children of the same age and sex, so the adult table above is not used for them. This calculator is not built for them.
- Risk can differ between populations. A 2004 WHO expert consultation found that a substantial proportion of Asian people have a high risk of type 2 diabetes and cardiovascular disease at BMIs below 25. It identified 23.0 and 27.5 as additional public health action points but kept the WHO cut-offs as the international classification. This calculator uses only the standard cut-offs.
- Pregnancy. This calculator is not designed for pregnancy. Ask your midwife or doctor how weight is assessed in your case.
BMI compared with other measures
| Measure | What it captures | Main limit |
|---|---|---|
| BMI | Weight relative to height | Does not separate fat from muscle or bone, or show where fat sits |
| Waist circumference | Fat carried around the middle | NHLBI says more than 35 inches (women) or 40 inches (men) increases risk; it needs a tape measure and a consistent method |
| Body fat percentage | Share of body weight that is fat | Needs a separate measurement or estimate; try our body fat calculator |
35 inches is about 88.9 cm and 40 inches is about 101.6 cm. The CDC says BMI is one measure that you and your health care provider can use alongside medical history, health behaviours, a physical exam and lab results to judge chronic disease risk.
What Is My BMI If...
What is my BMI if I am 5 ft 6 in and weigh 150 lb?
At 5 ft 6 in and 150 lb your BMI is 24.2, which is Normal weight. The calculator converts to 66 inches and 68.0 kg first. The healthy range for that height is 114.6 to 154.3 lb, so 150 lb is 4.3 lb below the top of the range.
What is my BMI if I am 5 ft 10 in and weigh 180 lb?
At 5 ft 10 in and 180 lb your BMI is 25.8, which is Overweight. The healthy range at 70 inches is 128.9 to 173.5 lb, so 180 lb is 6.5 lb above the top of the range. The weight at exactly BMI 25 for that height is about 174.2 lb.
What is my BMI if I weigh 70 kg and am 175 cm tall?
At 70 kg and 175 cm your BMI is 22.9, which is Normal weight. The calculation is 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.857. The healthy range for 175 cm is 56.7 to 76.3 kg.
What is my BMI if I weigh 65 kg and am 170 cm tall?
At 65 kg and 170 cm your BMI is 22.5, which is Normal weight. 170 cm is 1.70 m, and 1.70 × 1.70 = 2.89, so 65 ÷ 2.89 = 22.49. Anything from 53.5 to 72.0 kg at that height falls in the 18.5 to 24.9 range.
What is my BMI if I weigh 90 kg and am 180 cm tall?
At 90 kg and 180 cm your BMI is 27.8, which is Overweight. The healthy range at 180 cm tops out at 80.7 kg, so you are 9.3 kg above it. That gap is about 10.4% of 90 kg, which you can explore with the weight loss percentage calculator.
What is my BMI if I weigh 100 kg and am 175 cm tall?
At 100 kg and 175 cm your BMI is 32.7, which is Obese (Class 1). Class 1 covers 30 to less than 35. At 175 cm, BMI 35 starts at about 107.2 kg, and BMI 30 starts at about 91.9 kg.
What is my BMI if I am 5 ft 4 in and weigh 200 lb?
At 5 ft 4 in and 200 lb your BMI is 34.3, which is Obese (Class 1). You are just under the Class 2 threshold of 35. The healthy range at 64 inches ends at 145.1 lb, so the calculator shows you 54.9 lb above it.
What is my BMI if I am 6 ft 0 in and weigh 160 lb?
At 6 ft 0 in and 160 lb your BMI is 21.7, which is Normal weight. The healthy range at 72 inches is 136.4 to 183.6 lb. Because BMI divides by height squared, the same 160 lb gives a lower BMI at 6 ft 0 in than it does at 5 ft 6 in, where it would be 25.8.
What is my BMI if I weigh 50 kg and am 170 cm tall?
At 50 kg and 170 cm your BMI is 17.3, which is Underweight. The lowest weight in the healthy range at 170 cm is 53.5 kg, so you are 3.5 kg below it. A low BMI alone does not explain why, so a clinician can help you look at the whole picture.
What is my BMI if the result is just under 25?
A BMI of 24.98 is still Normal weight, because the category cut-off is 25. At 175 cm, 76.4 kg gives 24.9, 76.5 kg gives 24.98 and 76.6 kg gives 25.0 (Overweight). One kilogram changes BMI by about 0.33 at that height, so a result within a few tenths of a boundary is not a meaningful difference on its own.
People Also Search For
How to calculate BMI by hand
Divide your weight in kilograms by your height in metres squared, or multiply pounds by 703 and divide by inches squared. For 185 lb at 5 ft 9 in: 703 × 185 = 130,055, 69² = 4,761, and 130,055 ÷ 4,761 = 27.3. Keep all the digits until the last step and round only the final answer.
What is a healthy BMI range for adults
A BMI from 18.5 up to but not including 25 is the healthy weight range for adults. The CDC and the NHLBI both give this range, and this calculator uses a single adult table, so it does not ask for sex or age. Whether a number is right for you depends on factors a BMI cannot see, so ask your clinician.
BMI for children and teens
Children and teens are assessed with BMI-for-age percentiles, not the adult cut-offs. The CDC's child and teen calculator covers ages 2 through 19 and compares BMI with other children of the same age and sex. Its categories are underweight (below the 5th percentile), healthy weight (5th to below the 85th), overweight (85th to below the 95th) and obesity (95th or above). For anyone aged 2 through 19, use the CDC's child and teen BMI calculator.
BMI vs body fat percentage
BMI compares weight with height, while body fat percentage estimates how much of your weight is fat. Two people with the same BMI can have different body compositions. If you want a second view, try the body fat calculator alongside your BMI.
How much weight to lose to reach a healthy BMI
Multiply the top of the healthy range (BMI 24.9) by your height squared and compare it with your weight. At 5 ft 4 in (64 inches), 24.9 × (64 × 0.0254)² ÷ 0.45359 = 145.1 lb. If you weigh 200 lb, that is a gap of 54.9 lb, or about 27.5% of your weight. This is arithmetic, not a goal or a recommendation; a clinician can help set a realistic plan, and the calorie calculator can estimate your daily energy needs.
BMI cut-offs for Asian populations
The WHO kept its standard BMI cut-offs as the international classification, while finding that a substantial proportion of Asian people are at high risk at BMIs below 25. Its 2004 expert consultation identified 23.0 and 27.5 as further public health action points and left countries to decide how to define increased risk in their own populations. This calculator shows only the standard categories, so if you are of Asian descent, ask your clinician whether a different threshold applies to you.
Frequently Asked Questions
What is a good BMI?
For adults, a BMI from 18.5 to less than 25 is the healthy weight range in the CDC and NHLBI tables. BMI is a screening measure, so it should be read alongside other factors such as waist size, medical history and fitness. A clinician can tell you what is right for you.
Is BMI accurate for athletes and muscular people?
It can be misleading. The CDC notes that BMI does not distinguish between fat, muscle and bone mass, so a muscular person can have a high BMI without a high amount of body fat. In that case, a body fat estimate or a conversation with a clinician gives a clearer picture.
Does this calculator work for children and teenagers?
No. Children and teens are growing, so the CDC expresses their BMI as a percentile for their age and sex. This calculator uses the fixed adult cut-offs and is meant for adults aged 20 and over. For anyone aged 2 through 19, use the CDC's child and teen BMI calculator.
How accurate is this BMI calculator?
The arithmetic is exact: it converts pounds and inches precisely and applies weight ÷ height². The result is only as good as the numbers you enter, and BMI itself is a rough screening measure that cannot see muscle, bone or fat distribution.
What is the difference between BMI and body fat percentage?
BMI relates weight to height. Body fat percentage estimates the share of your weight that is fat. The CDC says BMI does not directly measure body fat, although it is moderately to strongly associated with other measures of it. You can estimate body fat with our body fat calculator.
What does a high BMI mean for my health?
A BMI of 25 or above is classed as overweight and 30 or above as obesity by the WHO. The CDC describes BMI as one measure that you and your health care provider can use to help judge chronic disease risk, together with your medical history and exam results. It is not a diagnosis, so talk to a clinician about what your number means for you.
What do obesity classes 1, 2 and 3 mean?
They are BMI bands within obesity: Class 1 is 30 to less than 35, Class 2 is 35 to less than 40, and Class 3 (severe obesity) is 40 or greater. The calculator shows the class next to "Obese" so you can see where you fall in the CDC table.
Can I use this calculator during pregnancy?
It is not designed for pregnancy, and its categories are the standard adult ones. If you are pregnant, ask your midwife or doctor how your weight should be assessed.
Why does waist circumference matter alongside BMI?
The WHO notes that waist circumference can also be used to identify overweight or obesity, and the NHLBI says a waist of more than 35 inches for women or more than 40 inches for men increases your risk. BMI cannot show where fat is carried, so the two measures complement each other.
How can I change my BMI?
Your BMI changes only when your weight changes, because adult height is fixed. Any plan to gain or lose weight is best made with a doctor or dietitian. For an estimate of daily energy needs, see the calorie calculator.
Which heights and weights does the calculator accept?
Heights from 50 cm to 300 cm (about 1 ft 8 in to 9 ft 10 in) and weights from 2 kg to 700 kg (about 4.4 lb to 1,543 lb). Outside those limits it asks you to check your entries, which usually catches a typing slip such as a missing digit.
Can I enter my height in inches only?
Yes. In imperial mode, leave feet blank and type the total inches, for example 69 for 5 ft 9 in. The calculator adds feet × 12 to the inches you enter.
Is my data stored or sent anywhere?
No. All calculations run in your browser. Nothing you type is sent to a server or saved, and no account is needed.
Sources
- CDC: Adult BMI categories
- CDC: About BMI
- CDC: Child and teen BMI calculator
- WHO: Obesity and overweight fact sheet
- NHLBI: Assessing your weight and health risk
- WHO Expert Consultation, Appropriate body-mass index for Asian populations, The Lancet 2004;363:157-163
This page is general information, not medical advice. It does not replace an assessment by a doctor or other qualified health professional.
Last reviewed: November 2026 — formulas and worked examples verified.