Metric BMI Calculator — Kilograms and Centimeters
The metric formula is the definition of BMI itself: weight (kg) ÷ height (m)². No conversion factor, because BMI is measured in kg/m². For adults the NHLBI puts the healthy range at 18.5 to 24.9, the same band used with pounds and inches.
Your BMI
22.9kg/m²
Weight within the healthy range for adults.
How we got this number
BMI = weight ÷ height² = 70 ÷ 1.70² = 22.9 kg/m²
Worked example
Someone 82 kg and 1.75 m: 1.75 × 1.75 = 3.0625, and 82 ÷ 3.0625 = 26.8 — the overweight range. The same person in US units is 180 lb and about 5 ft 9 in, which through 703 × 180 ÷ 69² gives 26.6. The small gap is rounding in the conversion, not a different index.
If your height is in centimeters, divide by 100 before squaring: 175 cm becomes 1.75 m. Squaring centimeters directly is the most common mistake with this formula, and it produces a number thousands of times too small.
Why two formulas exist for one index
BMI is defined in kilograms per square meter, and always has been. The 703 in the US version is pure unit conversion: it turns pounds per square inch into kg/m² so that the cutoffs still apply. There is no separate “American BMI” — the pounds and inches calculator is the same index with the conversion folded in.
This matters when you read research. Clinical literature reports BMI in kg/m², so a study that finds risk rising above 27 is talking about the same 27 this page produces.
The cutoffs, and one place they shift
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
These are the NHLBI adult ranges. One documented exception is worth knowing: several health authorities use lower overweight and obesity cutoffs for people of Asian descent, because cardiometabolic risk starts rising at a lower BMI in those populations. If that applies to you, the general table may read your risk as lower than it is — a reason to discuss the number with a clinician rather than to substitute one table for another on your own.
For a lookup by height instead of a calculation, see the BMI chart.
This content is informational and does not replace evaluation by a health professional.
Frequently asked questions
What is the metric BMI formula?
BMI = weight (kg) ÷ height (m)². Someone 82 kg and 1.75 m has a BMI of 82 ÷ (1.75 × 1.75) = 26.8. If you know your height in centimeters, divide by 100 first.
Why is there no 703 in the metric formula?
Because 703 is only a unit conversion. BMI is defined in kg/m²; the US formula multiplies by 703 to turn pounds and inches into that unit. Same index, same cutoffs, different input.
Which version should I use?
Whichever matches the numbers you already know. They give the same answer, so the only difference is whether you have to convert first. If you weigh yourself in pounds, use the pounds and inches calculator.
Are the healthy ranges different outside the US?
The 18.5 to 24.9 band is used internationally for adults. Some health authorities apply lower overweight cutoffs for people of Asian descent, because cardiometabolic risk rises at a lower BMI in those populations.
Sources
Written by Lucas Silva · Reviewed by Lucas Silva · Updated on August 13, 2026