BMI Calculator

Sex (for context)

Age

yrs

Height

Weight

MyWellnessCalc

BMI Calculator — Result

— BMI

—

UnderweightNormalOverweightObese

Underweight	Below 18.5
Normal weight	18.5 – 24.9
Overweight	25.0 – 29.9
Obese Class I	30.0 – 34.9
Obese Class II+	35.0 and above

What is BMI?

Body Mass Index (BMI) is a widely used screening tool that estimates whether a person's weight is appropriate for their height. It was developed by Belgian mathematician Adolphe Quetelet in the 19th century and is now used by healthcare providers worldwide as a quick, cost-free initial assessment.

BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg / m². The result falls into one of several categories defined by the World Health Organization (WHO).

Limitations of BMI

While BMI is useful as a population-level screening tool, it has important limitations. It does not directly measure body fat, and two people with the same BMI can have very different body compositions. Athletes often have a high BMI due to muscle mass, not excess fat. Similarly, BMI may underestimate health risk in older adults who have lost muscle mass.

BMI also does not account for where fat is distributed in the body — waist circumference is often a better predictor of metabolic risk.

What should I do with my result?

Use your BMI as a starting point for a conversation with your healthcare provider, not as a definitive diagnosis. If your BMI falls outside the normal range, consider also tracking waist circumference, reviewing your eating patterns, and consulting a registered dietitian or doctor for personalized guidance.

Healthy weight range by height

Working backwards from the formula gives the weight range that keeps an adult inside the 18.5–24.9 band at each height. These are the same cut-offs the calculator above uses.

Height	Healthy BMI weight (kg)	Healthy BMI weight (lb)
150 cm (4′11″)	42–56 kg	93–123 lb
155 cm (5′1″)	45–60 kg	100–132 lb
160 cm (5′3″)	48–63 kg	106–138 lb
165 cm (5′5″)	51–68 kg	113–149 lb
170 cm (5′7″)	54–72 kg	120–158 lb
175 cm (5′9″)	57–76 kg	126–167 lb
180 cm (5′11″)	60–80 kg	133–176 lb
185 cm (6′1″)	64–85 kg	142–187 lb
190 cm (6′3″)	67–90 kg	148–198 lb

The range is wide on purpose — at 170 cm it spans 18 kg. A number anywhere inside it says little on its own about health; where you sit within the band matters less than your waist size, fitness and blood markers.

BMI cut-offs for Asian adults

A 2004 World Health Organization expert consultation published in The Lancet found that in many Asian populations the BMI at which diabetes and cardiovascular risk rise is lower than in European populations — the observed risk threshold ranged from 22 to 25 depending on the population. Rather than redefining the categories, it kept the international cut-offs and added extra public health action points at 23, 27.5, 32.5 and 37.5. In practice, many Asian health services treat a BMI of 23 or above as a signal to look more closely at waist size, blood pressure and blood sugar.

A quick second check: waist-to-height ratio

BMI can't see where fat is carried. Since 2022, the UK's National Institute for Health and Care Excellence (NICE) has recommended that adults also measure their waist and aim to keep it to less than half their height — a waist-to-height ratio below 0.5. Measure halfway between the bottom of your ribs and the top of your hips, after breathing out normally. If your BMI is in the healthy range but your waist is more than half your height, that's worth raising with a doctor; if your BMI is high but your waist ratio is under 0.5, muscle may be part of the reason.

Children and teenagers

The adult categories don't apply under 18. For children and teens, BMI is compared against growth charts for the same age and sex and reported as a percentile, because healthy body fat changes as children grow.

Frequently asked questions

What is a healthy BMI for adults?

A healthy BMI for most adults is between 18.5 and 24.9. Below 18.5 is considered underweight, 25–29.9 is overweight, and 30 or above is classified as obese. These ranges apply to adults 18 and over.

Is BMI accurate for athletes and muscular people?

No. BMI cannot distinguish between fat and muscle. Muscular athletes often fall in the "overweight" or "obese" BMI range despite having very low body fat. For muscular individuals, body fat percentage is a more accurate health indicator.

How do I calculate BMI manually?

Divide your weight in kilograms by your height in metres squared. For example: 70 kg ÷ (1.75 × 1.75) = BMI of 22.9. In imperial units: multiply weight in pounds by 703, then divide by height in inches squared.

Does BMI differ for different ethnicities?

Yes. People of Asian descent may face increased health risks at lower BMI thresholds. Some health organisations recommend that a BMI of 23 or above (rather than 25) may indicate increased risk for people of Asian heritage.

What weight is healthy for my height?

For a BMI of 18.5–24.9, it's roughly 54–72 kg (120–158 lb) at 170 cm (5′7″), 60–80 kg (133–176 lb) at 180 cm (5′11″) and 48–63 kg (106–138 lb) at 160 cm (5′3″). The table on this page lists heights from 150 to 190 cm.

Is waist size more important than BMI?

It adds information BMI can't provide, because it reflects fat stored around the organs. NICE recommends keeping your waist to less than half your height (a waist-to-height ratio under 0.5) alongside checking BMI. Using both together gives a better picture than either alone.

Sources

World Health Organization. Obesity and overweight — fact sheet.
WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet 2004;363:157–163. thelancet.com
National Institute for Health and Care Excellence. Keep the size of your waist to less than half of your height, NICE recommends (2022).

Not medical advice. This calculator is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before making decisions about your diet, exercise, or health.