BMI Calculator
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Find your BMI, category and healthy weight for your height, in kilograms and centimeters or pounds, feet and inches. The same cut-offs apply to women and men, and the steps are shown.
Quick answer: A BMI of 18.5 to 24.9 is the healthy range for adults under the CDC's adult categories, 25 to 29.9 is overweight and 30 or more is obesity. This BMI calculator uses BMI = weight (kg) ÷ height (m)², or 703 × weight (lbs) ÷ height (in)², and the same cut-offs apply to women and men. For anyone younger than 20, BMI is read against age and sex percentiles instead.
Your BMI
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ℹ️ BMI is a screening tool, not a diagnosis. It does not account for muscle mass, bone density, age or fat distribution. Ask a doctor for a health assessment.
📐 BMI formula
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lbs) ÷ height (in)². Mixed units, such as kg with feet and inches, are converted to kilograms and meters first. The calculator rounds to one decimal place, then reads the category from that figure.
How to use the BMI calculator
Choose your units
Pick kilograms or pounds for weight and centimeters or feet and inches for height. The two are chosen separately, so kilograms with feet and inches works. The inches box can stay blank if your height is a whole number of feet.
Enter your weight and height
Use your current weight and your height without shoes. The calculator shows a message instead of a result if a figure is outside 10 to 500 kg and 50 to 272 cm (22 to 1,100 lbs and 1 ft 8 in to 8 ft 11 in).
Optional: add your age, sex and background
None of these changes the BMI number. Age adds a note for ages under 20 and for ages 65 and over, sex adds a body-composition note, and choosing Asian descent adds the weight at a BMI of 23 for your height.
Read your BMI and healthy range
The result shows your BMI, its category, the weight range that gives a BMI of 18.5 to 24.9 at your height, and how far you are from that range. The steps sit under the result.
Treat it as a screening number
BMI cannot tell muscle from fat. Pair it with your waist measurement or body fat, and ask a doctor before you change your diet or your weight.
What is a healthy BMI?
This is a BMI calculator for adults aged 20 and over: for ages under 20 it gives the number but no adult category. For adults, the CDC puts the healthy range at a BMI of 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more is obesity, which the CDC splits into three classes. The WHO uses the same 25 and 30 cut-offs. There is one set of cut-offs for adults, so the chart below serves women and men alike. The chart's weights are rounded to whole numbers, so a BMI within 0.05 of a boundary can land in a different category than the chart suggests. The calculator reads the category from the one-decimal BMI.
| BMI (kg/m²) | Category | Weight at 5 ft 7 in |
|---|---|---|
| Below 18.5 | Underweight | 118 lbs (53 kg) or less |
| 18.5 to 24.9 | Healthy weight | 119 to 159 lbs (54 to 72 kg) |
| 25.0 to 29.9 | Overweight | 160 to 191 lbs (73 to 86 kg) |
| 30.0 to 34.9 | Obesity, Class 1 | 192 to 223 lbs (87 to 101 kg) |
| 35.0 to 39.9 | Obesity, Class 2 | 224 to 255 lbs (102 to 115 kg) |
| 40.0 and above | Obesity, Class 3 | 256 lbs (116 kg) or more |
BMI describes a group better than it describes you. It was devised by the Belgian mathematician Adolphe Quetelet in the 1830s to compare populations, and it still works best as a first screen: a number that tells you whether to look closer, not a verdict.
What is a healthy BMI for women and for men?
The same: 18.5 to 24.9. The formula only uses height and weight, so a woman and a man at 5 ft 7 in and 150 lbs both get a BMI of 23.5. What differs is what that number sits on. At the same BMI, women carry more body fat than men and older adults carry more than younger ones (Gallagher and colleagues, 1996). That is why choosing a sex here adds a note under your result instead of changing the figure.
Healthy BMI by age: adults, over 65, kids and teens
Adults aged 20 to 64
The standard table above applies, whatever your age or sex within this group. The CDC says its adult categories hold for adults aged 20 and over. Adults over 60 who are not yet 65 get the same cut-offs.
Adults aged 65 and over
The cut-offs do not change, but they fit older adults less neatly. A 2014 meta-analysis of adults aged 65 and over found no higher risk of death in the overweight range and a higher risk at the lower end of the healthy range, around BMI 20 to 22 (Winter and colleagues). Muscle loss also means an older adult can have a healthy-looking BMI and still carry too much fat. Ask your doctor which range suits you, and take unplanned weight loss seriously.
Kids and teens aged 2 to 19
Children are still growing, so the CDC compares a child's BMI with other children of the same age and sex and reports a percentile: below the 5th is underweight, the 5th to below the 85th is a healthy weight, the 85th to below the 95th is overweight, and the 95th or above is obesity. This calculator still gives the BMI number if you enter an age under 20, but it will not apply the adult category. Use the CDC child and teen BMI calculator for the percentile.
BMI for people of Asian descent
Health risks can rise at lower BMIs in some Asian populations. A 2004 WHO expert consultation looked at the evidence, kept the international cut-offs of 25 and 30, and identified 23.0 and 27.5 as additional public health action points. It proposed ways for each country to decide how to define increased risk for its own population. This calculator's category follows the international cut-offs. If you choose Asian descent in the Background box, it also shows the weight that gives a BMI of 23.0 at your height.
Healthy weight by height
The healthy range of 18.5 to 24.9 turns into a different weight at every height. The table lists common heights, with each weight worked out from the height in inches and rounded to the nearest whole unit (the centimeter heights are rounded too). For a 157 cm (5 ft 2 in) woman or man, the healthy range is about 46 to 62 kg (101 to 136 lbs). A woman who is 5 ft 5 in (165 cm) has a healthy range of about 111 to 150 lbs (50 to 68 kg), rounded the same way. The calculator above gives the range for your exact height.
| Height | Weight (lbs) | Weight (kg) |
|---|---|---|
| 4 ft 10 in (147 cm) | 89–119 lbs | 40–54 kg |
| 5 ft (152 cm) | 95–128 lbs | 43–58 kg |
| 5 ft 2 in (157 cm) | 101–136 lbs | 46–62 kg |
| 5 ft 4 in (163 cm) | 108–145 lbs | 49–66 kg |
| 5 ft 6 in (168 cm) | 115–154 lbs | 52–70 kg |
| 5 ft 8 in (173 cm) | 122–164 lbs | 55–74 kg |
| 5 ft 10 in (178 cm) | 129–174 lbs | 58–79 kg |
| 6 ft (183 cm) | 136–184 lbs | 62–83 kg |
| 6 ft 2 in (188 cm) | 144–194 lbs | 65–88 kg |
| 6 ft 4 in (193 cm) | 152–205 lbs | 69–93 kg |
How to calculate BMI by hand
Metric. Square your height in meters, then divide your weight in kilograms by that figure. For 70 kg at 1.75 m: 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.86, which rounds to 22.9, inside the healthy range. For 75 kg at the same height: 75 ÷ 3.0625 = 24.49, or 24.5, still inside the healthy range but close to the top.
Imperial. Multiply your weight in pounds by 703, then divide by your height in inches squared. For 154 lbs at 5 ft 9 in (69 inches): 703 × 154 = 108,262, and 69 × 69 = 4,761, so 108,262 ÷ 4,761 = 22.74, or 22.7. That differs slightly from the metric example only because 154 lbs and 69 inches are not exactly 70 kg and 1.75 m.
Mixed units. A mix of kg and feet is common. If your weight is in kilograms but your height is in feet and inches, convert the height first: multiply the inches by 0.0254 to get meters. For 70 kg at 5 ft 9 in (69 inches): 69 × 0.0254 = 1.7526 m, then 1.7526 × 1.7526 = 3.0716, and 70 ÷ 3.0716 = 22.79, or 22.8. The calculator does this conversion for you and shows it in the steps. Pounds with centimeters works the same way, with the weight converted to kilograms first (1 lb = 0.45359237 kg).
Rounding and the boundaries. The calculator rounds BMI to one decimal place and reads the category from that figure, so a BMI of 24.96 shows as 25.0 and counts as overweight. Height matters more than most people expect, because it is squared. Recording 1.75 m as 1.73 m moves a 70 kg person from 22.86 to 23.39, which is enough to change the category near a boundary. Measure without shoes, standing fully upright.
Limitations of BMI: what it does not measure
BMI cannot tell muscle from fat, so it overstates fatness in muscular people and understates it in older adults who have lost muscle. It also ignores where fat sits, and the NHS advises adults with a BMI under 35 to keep their waist below half their height. In one large US analysis, a BMI of 30 or more picked up only 36% of men and 49% of women whose body fat was in the obese range (Romero-Corral and colleagues, 2008). A high BMI is a strong signal. A normal one is not proof of good health.
For a second number, try the body fat calculator, or divide your waist measurement by your height, the ratio from the NHS advice above.
Once you know your range, the ideal weight calculator gives target weights by formula, the BMR calculator estimates the calories you burn at rest, and the calorie calculator turns that into a daily target.
Pregnancy is a special case: the pregnancy question in the FAQ below says which BMI to use.
Using this BMI calculator in the US, UK and Canada
The formula is the same everywhere, and you can enter your figures in kilograms and centimeters or pounds, feet and inches. UK readers who weigh themselves in stones can multiply by 14 and add the pounds: 10 stone 4 lb is 144 lbs. In the US, the adult categories are the CDC's (18.5, 25 and 30), and the CDC's child and teen percentiles apply under age 20. The same international cut-offs are used here for everyone. As read on November 4, 2026, the NHS uses lower thresholds (23 and 27.5) for people from South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds. The Asian-descent option above shows the weight at a BMI of 23. Canadians can also use our BMI calculator for Canada, which adds a waist circumference check.
Frequently asked questions
BMI is a quick screening tool, not a diagnosis. A high BMI usually does point to excess body fat, but a BMI in the healthy range can still hide it, and BMI says nothing about fitness, blood pressure, blood glucose or cholesterol. Discuss your whole health profile with your doctor.
A BMI of 18.5 to 24.9, for adults aged 20 and over. Anything inside that range counts as a healthy weight on BMI alone, so a BMI of 19 and a BMI of 24 fall in the same category. If you want a single target weight, the ideal weight calculator gives one by formula.
BMI uses only height and weight, so it cannot separate people whose bodies differ. Take two people at 5 ft 9 in and 190 lbs, one a lifter and one inactive: both get a BMI of 28.1.
Yes. The formula uses only height and weight, so 60 kg at 1.65 m gives a BMI of 22.0 for a woman or a man, and both are in the healthy range.
A BMI of 30 or more is classed as obesity, in three classes: 30 to 34.9 (Class 1), 35 to 39.9 (Class 2) and 40 or more (Class 3, also called severe obesity). At 6 ft, a BMI of 30 is about 221 lbs (100 kg). These cut-offs apply to adults aged 20 and over.
Not reliably. BMI only sees height and weight, so 20 lbs of added muscle raises it exactly as 20 lbs of fat would: at 5 ft 9 in, about 3 BMI points. A waist measurement or a body fat percentage shows which one you gained.
No. The BMI formula is the same for everyone: weight divided by height squared. Entering your age, sex or Asian descent adds a note under the result. It does not change the number.
There is no single healthy number, because the same BMI means different things at 8 and at 15. A child at the 60th percentile has a BMI higher than 60 out of 100 children of the same age and sex.
No. The published cut-offs stay the same whether you are 40 or 80, and the calculator's age note starts at 65. For older adults the trend tells you more than one reading: a weight that falls without trying matters more than a single number, so keep a record and show it to your doctor.
You can enter your weight, but a BMI taken during pregnancy does not show whether your weight is healthy. Recommended weight gain in pregnancy is based on your BMI before pregnancy, so enter your pre-pregnancy weight to see that BMI, and ask your doctor or prenatal care provider for your weight gain target.
Work backwards from the formula: multiply 18.5 and 24.9 by your height in meters squared. At 1.80 m that is 3.24, so the range is about 60 to 81 kg. The calculator does this for any height you enter, using the edges of the one-decimal categories, so at 180 cm it shows 59.8 to 80.8 kg.
Sources & Methodology
The category cut-offs are the CDC adult definitions, which match the WHO's 25 and 30. BMI is computed as weight in kilograms divided by height in meters squared (or 703 × pounds ÷ inches squared), rounded to one decimal place, and the category is read from that rounded figure. The healthy weight range uses BMI 18.5 to 24.9 at your height.
- CDC: Adult BMI categories
- CDC: Child and teen BMI categories (percentiles)
- CDC: Child and teen BMI calculator
- WHO: Obesity and overweight fact sheet
- WHO expert consultation: Appropriate body-mass index for Asian populations. The Lancet, 2004
- Gallagher D et al. How useful is body mass index for comparison of body fatness across age, sex, and ethnic groups? Am J Epidemiol, 1996
- Winter JE et al. BMI and all-cause mortality in older adults: a meta-analysis. Am J Clin Nutr, 2014
- NHS: Obesity (waist-to-height advice and BMI thresholds by background)
- Romero-Corral A et al. Accuracy of body mass index in diagnosing obesity in the adult general population. Int J Obes, 2008