BMI Calculator – Body Mass Index

Enter your height and weight to calculate your Body Mass Index instantly. This free BMI calculator supports both the standard international chart and the lower Asian cut-offs many clinicians use for patients of Asian descent.

How to Use the BMI Calculator

Using this calculator takes less than ten seconds. First, measure your height in centimeters — stand straight against a wall without shoes for the most accurate reading. Next, weigh yourself in kilograms, ideally in the morning before breakfast and wearing light clothing, since food, water and heavy clothes can shift the number by a kilogram or more.

Enter both numbers in the boxes above and choose which BMI chart you want to use. If you are of Asian descent, consider selecting the Asian cut-offs option: research shows that conditions like type 2 diabetes and heart disease tend to appear at lower BMIs in Asian populations, so many clinicians use stricter thresholds for these patients. Press Calculate BMI and you will see your index, your weight category, and the healthy weight range for your height.

BMI Formula

Body Mass Index is your weight in kilograms divided by the square of your height in meters. It was devised in the 1830s by the Belgian statistician Adolphe Quetelet as a quick way to compare body sizes across populations, and it remains the most widely used screening measure in the world.

Because most of us measure height in centimeters, the calculator first converts centimeters to meters by dividing by 100, then applies the formula. No other personal data is needed, which is exactly why BMI became so popular — it is simple, free and needs no equipment beyond a tape measure and a scale.

Worked Example

Let us walk through a real calculation for a person who is 170 cm tall and weighs 70 kg:

Notice the last row: the same person is "Normal" on the international chart but "Overweight" on the Asian chart. This is precisely why the chart selector matters — an adult of Asian descent with a BMI of 24.2 may already be advised to watch their diet and activity level, while the standard chart would call them fine.

Standard vs Asian BMI Chart — What Most Calculators Don't Tell You

Almost every BMI calculator on the internet uses only the standard WHO cut-offs. But in 2004, after reviewing evidence from across Asia, the World Health Organization noted that Asian populations face elevated health risks at lower BMIs and suggested lower action points. Many hospitals and clinics now counsel patients of Asian descent using these tighter bands.

The practical takeaway: if your BMI is between 23 and 25, standard charts call you healthy, but Asian guidance says you are already in the overweight zone where lifestyle changes pay off most. This calculator is one of the few free tools that lets you check both.

The same lower-risk-threshold pattern is noted for other groups too: some clinical guidance notes health risks rising from a BMI of around 23 for South Asian, East Asian, Black African and Middle Eastern groups, and some services ask about ethnic background when giving BMI advice. That is a reason to treat any single cut-off as a starting point, not a verdict — BMI cannot distinguish muscle from fat, so athletes and very muscular people can read as 'overweight' while carrying low body fat, and it says nothing about where fat is stored. Pair the result with a waist measurement and a clinician's view, especially if you are near a threshold.

Limitations of BMI

BMI is a screening tool, not a diagnosis. It cannot tell muscle apart from fat, so athletes, bodybuilders and people with physically demanding jobs can land in the "overweight" band while being perfectly fit. Conversely, older adults can have a "normal" BMI yet carry too much body fat and too little muscle — a condition sometimes called normal-weight obesity.

BMI also says nothing about where fat is stored. Belly fat around the waist is more strongly linked to heart disease and diabetes than fat on the hips and thighs, which is why doctors often pair BMI with a simple waist measurement: above 40 inches (102 cm) for men and above 35 inches (88 cm) for women is considered a risk flag. Pregnant women and children should not use adult BMI cut-offs at all. Treat your result as a starting point for a conversation with a healthcare professional, not a verdict.

A BMI number is a starting point, not a verdict — the BMR calculation guide takes the next step, turning your stats into calorie targets with the Mifflin-St Jeor formula. And if you are documenting progress with photos, the Watermark Cover-Up tool lets you cover logos, faces or gym signage on your own pictures before they go anywhere public.

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