Important: Not medical advice. This report is a general estimate from a published formula. It is not medical advice, a diagnosis, or a treatment plan, and it doesn't account for your health history, medications, pregnancy or other conditions. Talk to a doctor, midwife or registered dietitian before making health decisions based on it. Use of this report is at your own risk; see aiocalc.com/disclaimer and aiocalc.com/terms.

Health

BMI Calculator

Calculate your body mass index from your height and weight, see which adult category it falls in, and find the healthy weight range for your height. Works in US or metric units.

Updated October 11, 2026 · 3 cited sources

Your details

Your BMI

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kg/m² · —

Enter your height and weight to see your BMI.

Where you fall

Healthy weight for your height

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To reach healthy range

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BMI Prime

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BMI ÷ 25; above 1.0 is overweight

Show the math

BMI = weight (kg) ÷ height (m)² · or 703 × weight (lb) ÷ height (in)²

Screening estimate only, not medical advice. BMI doesn't measure body fat directly and doesn't apply to children, pregnant people, or very muscular adults in the same way.

What is BMI?

Body mass index is your weight divided by the square of your height. It was designed for studying populations, and it's still the standard first screen for weight-related health risk because it needs nothing more than a scale and a tape measure. Higher BMIs are linked with higher rates of type 2 diabetes, high blood pressure, heart disease and some cancers; very low BMIs are linked with nutritional deficiency and bone loss.

A BMI is a screening number, not a diagnosis. It flags who might benefit from a closer look, such as a waist measurement, blood tests or a conversation with a doctor.

Adult BMI categories

The CDC and WHO use the same cut-points for adults 20 and older, regardless of sex or age:

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)

BMI is reported to one decimal place, and the category follows that rounded number, so a BMI of 24.96 shows as 25.0 and counts as overweight. Some health agencies use lower cut-points for people of Asian descent, whose diabetes risk rises at lower BMIs; WHO suggests 23 as a point for public-health action in those populations.

Healthy weight by height

Weight ranges for each adult category at common heights, computed from the same cut-points the calculator uses. Find your height, then read across.

Weight ranges by height for healthy weight, overweight and obesity
Height	Healthy (18.5–24.9)	Overweight (25–29.9)	Obesity (30+)
4 ft 10 in (147 cm)	89–119 lb	120–143 lb	144+ lb
4 ft 11 in (150 cm)	92–123 lb	124–148 lb	149+ lb
5 ft 0 in (152 cm)	95–127 lb	128–153 lb	154+ lb
5 ft 1 in (155 cm)	98–132 lb	133–158 lb	159+ lb
5 ft 2 in (157 cm)	101–136 lb	137–163 lb	164+ lb
5 ft 3 in (160 cm)	105–140 lb	141–169 lb	170+ lb
5 ft 4 in (163 cm)	108–145 lb	146–174 lb	175+ lb
5 ft 5 in (165 cm)	111–149 lb	150–179 lb	180+ lb
5 ft 6 in (168 cm)	115–154 lb	155–185 lb	186+ lb
5 ft 7 in (170 cm)	118–159 lb	160–191 lb	192+ lb
5 ft 8 in (173 cm)	122–164 lb	165–196 lb	197+ lb
5 ft 9 in (175 cm)	125–168 lb	169–202 lb	203+ lb
5 ft 10 in (178 cm)	129–173 lb	174–208 lb	209+ lb
5 ft 11 in (180 cm)	133–178 lb	179–214 lb	215+ lb
6 ft 0 in (183 cm)	137–183 lb	184–220 lb	221+ lb
6 ft 1 in (185 cm)	140–189 lb	190–227 lb	228+ lb
6 ft 2 in (188 cm)	144–194 lb	195–233 lb	234+ lb
6 ft 3 in (191 cm)	148–199 lb	200–239 lb	240+ lb
6 ft 4 in (193 cm)	152–204 lb	205–246 lb	247+ lb

BMI for women and men

There's no separate BMI calculator for women or men: adults use one formula and one set of categories. What differs is what a given BMI looks like. At the same BMI, women on average carry more body fat than men, and men carry more muscle. That's one reason a waist measurement or a body fat estimate is a useful second opinion. During pregnancy BMI isn't meaningful; doctors use pre-pregnancy BMI to set weight-gain targets instead.

BMI by age, children and teens

Adult categories apply from age 20 and don't change with age after that. For children and teens aged 2 to 19, the same BMI number is compared with CDC growth charts for their age and sex, because body fat changes as kids grow and differs between boys and girls. A child is classed as having obesity at or above the 95th percentile and overweight from the 85th to below the 95th. This calculator doesn't compute percentiles, so use the CDC's child-and-teen calculator for anyone under 20.

What BMI can't tell you

Muscle vs. fat. Muscle is denser than fat, so athletes and people who lift can score as overweight with little body fat.
Where fat sits. Fat around the waist carries more risk than fat on the hips. A waist over 40 in for men or 35 in for non-pregnant women is a separate warning sign.
Age-related muscle loss. Older adults can have a healthy BMI while carrying more fat and less muscle than the number suggests.
Ethnicity. Health risk rises at lower BMIs in some populations, notably people of South and East Asian descent.

How BMI is calculated

In metric units, BMI = weight (kg) ÷ height (m)². For 70 kg at 1.75 m that's 70 ÷ 3.0625 = 22.9. In US units the formula needs a conversion factor: BMI = 703 × weight (lb) ÷ height (in)². This calculator converts pounds and feet to kilograms and meters first, so both unit systems give the same answer. The healthy weight range is 18.5 × height² to 24.9 × height², and BMI Prime is your BMI divided by 25, the top of the healthy range.

Sources

The formulas on this page come from the published research below. Last updated October 11, 2026. This calculator gives estimates for general information. It isn't medical advice, so check anything important with a qualified professional.

Centers for Disease Control and Prevention. Adult BMI Categories.Used for: Adult BMI cut-points (18.5, 25, 30, 35, 40) and obesity classes 1–3, for adults 20 and older regardless of sex or age
World Health Organization. Obesity and overweight (fact sheet).Used for: BMI definition (kg/m²) and the international overweight (≥25) and obesity (≥30) thresholds
Centers for Disease Control and Prevention. BMI Percentile Calculator for Child and Teen.Used for: Percentile-based BMI categories for ages 2–19

Frequently asked questions

Is the BMI calculator accurate?

The arithmetic is exact: BMI is just weight divided by height squared. What's approximate is what the number says about you. BMI tracks body fat reasonably well across large groups, which is why the CDC and WHO use it for screening, but it can't tell muscle from fat. A muscular athlete can read as overweight and an older adult who has lost muscle can read as healthy while carrying excess fat. Treat it as a first check, not a diagnosis.

What's the difference between BMI and body fat percentage?

BMI only uses height and weight, so it measures how heavy you are for your height. Body fat percentage estimates how much of that weight is fat. Two people with the same BMI can have very different body fat. For a closer look, the body fat calculator uses the US Navy tape-measure method, and waist circumference adds information BMI misses: the CDC flags a waist over 40 in (men) or 35 in (non-pregnant women) as a higher health risk.

Is BMI different for women and men?

No. Adults 20 and older use the same formula and the same categories regardless of sex. Women typically carry more body fat than men at the same BMI, so the same number doesn't mean the same body composition, but the screening cut-points are shared. Sex only enters the picture for children and teens, whose BMI is compared with sex-specific growth charts.

Does BMI change with age?

For adults the categories don't change with age. Some research suggests the lowest health risk for adults over 65 sits slightly higher than for younger adults, partly because a little extra weight can be protective against frailty, but official adult categories are the same at 25 and 75. Under 20, BMI is read as a percentile for age and sex instead.

What should I do if my BMI is outside the healthy range?

Use it as a reason to look closer, not a verdict. A doctor can combine BMI with waist size, blood pressure, blood sugar and cholesterol to judge actual risk. If you decide to change your weight, the calorie and TDEE calculators give a daily target, and aiming for 1–2 lb a week is what the CDC describes as gradual, sustainable loss.