A metric BMI calculator computes Body Mass Index from height in centimeters and weight in kilograms using the clean form of the formula: BMI = kg ÷ m². Enter your height and weight; the calculator returns a single BMI number plus the category bands.
This is the same BMI used worldwide, only the input units differ from the imperial-input version. The metric formula is the original one (Quetelet, 1832); the US-customary version with the 703 factor is just a unit-conversion derivative.
Key takeaway
BMI is a population-scale screening tool, not a body-composition measurement. It treats weight as a proxy for body fat, which works on average but breaks down for muscular individuals, very tall or very short people, the elderly, and across some ethnic groups. Treat the number as one input, not a verdict.
How it's calculated
The metric formula:
BMI = weight (kg) ÷ height (m)²
Note height is in meters, not centimeters, divide cm by 100 before squaring. So a 175 cm tall person uses 1.75 m → 1.75² = 3.0625. A 75 kg weight gives BMI = 75 ÷ 3.0625 = 24.5.
The four standard adult categories (WHO):
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese (Class I/II/III) |
The WHO has noted that for East and Southeast Asian populations, cardiovascular risk increases at lower BMI thresholds, some Asian countries use 23 instead of 25 as the overweight cutoff and 27.5 as the obese threshold. Singapore, Hong Kong, and several other jurisdictions follow these adjusted bands.
Source: WHO adult BMI categories
Examples
175 cm, 75 kg, typical adult
- Height 175 cm
- Weight 75 kg
At 175 cm (5'9") and 75 kg (165 lb), BMI is 24.5, within the normal range, near the upper boundary. Gaining 2 kg would push the BMI past 25 into the overweight band. This is roughly the average European male body type for the WHO data.
165 cm, 60 kg, average European female adult
- Height 165 cm
- Weight 60 kg
At 165 cm (5'5") and 60 kg (132 lb), BMI is 22.0, solidly in the normal range. The full normal-weight band for this height runs from ~50 kg (BMI 18.5) to ~68 kg (BMI 24.9), about a 18 kg spread. BMI's coarseness shows here: significant body-comp variation can fit within the same band.
Frequently asked questions
How do I calculate BMI in metric?
BMI = weight (kg) ÷ height (m)². Convert your height from cm to m by dividing by 100, then square it. So 170 cm = 1.70 m; 1.70² = 2.89; if you weigh 70 kg, BMI = 70 ÷ 2.89 = 24.2. Or skip the conversion and use the equivalent form: BMI = weight (kg) × 10,000 ÷ height (cm)².
Is the metric BMI different from the imperial BMI?
No, they're the same metric. The metric formula is kg/m²; the imperial-input version (lb × 703 / in²) just adds the 703 factor to handle unit conversion. Both produce the same BMI number for the same person; only the inputs differ. Most clinical and scientific literature worldwide uses the metric form.
Why do some Asian countries use different BMI cutoffs?
Because research on East and Southeast Asian populations shows cardiovascular and metabolic risk rising at lower BMI thresholds than the standard WHO bands suggest. Several Asia-Pacific bodies use 23 as the overweight cutoff and 27.5 as the obese cutoff, about 1.5-2.5 BMI units below the global standard. Singapore, Hong Kong, India, and several other jurisdictions follow these adjusted bands. The idea is to flag elevated risk earlier in populations that show metabolic effects of higher body fat at lower BMIs.
Should I use BMI to track weight loss progress?
It works as one signal among many. Body fat percentage and waist circumference are typically more sensitive to changes in body composition during weight loss, especially because resistance training during a cut preserves or builds muscle, which keeps BMI roughly stable while body composition improves. Track BMI weekly or monthly, but don't rely on it as the only measure. Photos, measurements, and how clothes fit complement the number.