BMI Calculator

Calculate your body mass index and find out your weight category and ideal healthy weight range

Unit system

Metric (kg / cm) Imperial (lbs / ft)

Weight (kilograms)

Height (centimeters)

How to use the BMI Calculator

Choose your unit system

Select metric (kg/cm) or imperial (lbs/ft+in) depending on your preference.

Enter your weight and height

Enter your current weight and height accurately for a correct result.

Press Calculate

Your BMI value, weight category, and healthy weight range appear instantly.

Read the result

The colour scale shows where your BMI sits among the four WHO categories.

BMI classification table (WHO)

The World Health Organization uses the following classification for adults. The calculator above shows your category automatically once you enter height and weight:

BMI value	Classification	Risk level
< 18.5	Underweight	Increased (malnutrition, bone loss)
18.5 – 24.9	Normal weight	Lowest
25.0 – 29.9	Overweight	Slightly increased
30.0 – 34.9	Obesity class I	Increased
35.0 – 39.9	Obesity class II	High
≥ 40.0	Obesity class III (severe)	Very high

Healthy weight by height

There is no single "ideal weight" — there is a healthy range for each height. The ranges below are calculated at a BMI between 18.5 and 24.9:

Height	Healthy weight range
150 cm	41.6 – 56.0 kg
155 cm	44.4 – 59.8 kg
160 cm	47.4 – 63.7 kg
165 cm	50.4 – 67.8 kg
170 cm	53.5 – 72.0 kg
175 cm	56.7 – 76.3 kg
180 cm	59.9 – 80.7 kg
185 cm	63.3 – 85.2 kg
190 cm	66.8 – 89.9 kg

The table is for adults and does not account for muscle mass or frame size. The calculator above shows the exact range for your own height once you press Calculate.

The limits of BMI

BMI is a quick screening tool, not a diagnosis. It does not measure fat directly and does not distinguish fat from muscle, bone, or body water, so it gets certain cases wrong:

Athletes — muscle is denser than fat, so an athlete in excellent health can be classified as overweight.
Older adults — muscle loss with age can keep BMI in the normal range even when body fat is genuinely high.
Children and teenagers — they need age- and sex-specific percentile growth charts, not the fixed adult cutoffs.
Pregnancy — normal pregnancy weight gain makes the index meaningless for that period.
Fat distribution — BMI cannot tell riskier abdominal fat from fat elsewhere, which is why waist circumference is recommended alongside it.

Waist circumference and the Asian thresholds

Waist circumference measures abdominal fat specifically, the type most closely linked to heart disease and type 2 diabetes. The WHO treats 94 cm or more for men and 80 cm or more for women as increased risk, and 102 cm for men and 88 cm for women as substantially increased. It is entirely possible to have a normal BMI and a raised waist measurement at the same time.

The BMI thresholds themselves were originally derived from studies on European populations. Later research found metabolic risk begins at lower values in Asian populations, so some Asian guidelines treat 23 as the overweight threshold and 25 as the obesity threshold rather than 25 and 30. This calculator shows the global WHO classification; if your value falls between 23 and 25, it may be worth raising with your doctor.

Frequently Asked Questions about BMI

Divide your weight in kg by your height in metres squared. Example: 70 kg and 1.75 m → BMI = 70 ÷ (1.75²) = 22.9.

According to the WHO: below 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, and 30 or above is obese.

BMI is a general screening tool, not a precise medical measurement. It cannot distinguish fat from muscle, so athletes may have a high BMI without being overweight. Consult your doctor for a complete evaluation.

The calculator automatically shows your healthy weight range for your height when you press Calculate. The healthy range is the weight that gives a BMI between 18.5 and 24.9.

Yes, the BMI calculator is completely free and runs in your browser with no signup or data upload required.

The healthy range at 170 cm is 53.5 to 72 kg, which gives a BMI between 18.5 and 24.9. At 160 cm it is 47.4 to 63.7 kg, and at 180 cm it is 59.9 to 80.7 kg. See the healthy-weight-by-height table above for other heights.

Not exactly. The global cutoffs (25 and 30) were developed from studies on European populations, and later research found metabolic risk begins at lower values in Asian populations. Some Asian guidelines therefore treat 23 as the overweight threshold and 25 as the obesity threshold. Treat the difference as a prompt to look earlier, not as a diagnosis.

Waist circumference measures abdominal fat specifically, which is the most strongly linked to heart disease and type 2 diabetes. The WHO treats 94 cm or more for men and 80 cm or more for women as increased risk, and 102 cm for men and 88 cm for women as substantially increased. You can have a normal BMI and a raised waist measurement at the same time.

No. The WHO classification used here applies to adults aged 20 and over. For children and teenagers, BMI is assessed against age- and sex-specific percentile growth charts, because body composition changes through the stages of growth. See a paediatrician to assess a child's weight.

BMI is not used during pregnancy, because the normal weight gain includes the baby, amniotic fluid, the placenta, and increased blood volume. Clinical practice is to use pre-pregnancy BMI to set the recommended gain range, then track it with the doctor managing the pregnancy.

Source: WHO classification (2004) — BMI = weight (kg) ÷ height² (m). Categories: <18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, ≥30 obese. Last verified: 26 May 2026. BMI is a general screening indicator, not a substitute for medical evaluation.

About the BMI Calculator

Body Mass Index (BMI) is a universally recognised screening measure calculated by dividing weight in kilograms by the square of height in metres (weight ÷ height²). The World Health Organization (WHO) has adopted this index as a standard tool for classifying weight status in adults: underweight below 18.5, normal weight 18.5–24.9, overweight 25–29.9, Class I obesity 30–34.9, Class II obesity 35–39.9, and severe obesity 40 and above. Doctors and healthcare providers worldwide use BMI as a starting point for assessing the risk of weight-related conditions such as type 2 diabetes, cardiovascular disease, and hypertension. The calculation is performed entirely in your browser without saving any data. Also try the Percentage Calculator for other quick calculations.

BMI does not distinguish between fat, muscle, and bone, so it may not reflect the full picture for athletes or older adults. Consult a doctor or registered dietitian for a comprehensive assessment that also accounts for factors such as waist circumference and body-fat percentage.

For percentage calculations on weight or calories, try the percentage calculator. Everything is computed inside your browser — no health data is stored or sent to any server.