BMI Calculator — Metric Guide (kg and cm)

The standard BMI formula was originally defined in metric units — kilograms and meters. If you use metric measurements (most of the world outside the US), the formula is more straightforward: no conversion factor needed. The free BMI calculator supports both metric (kg and cm) and imperial — select your unit system with the toggle at the top.

The Metric BMI Formula — kg and m

BMI = weight in kilograms ÷ (height in meters)²

Height must be in meters, not centimeters. Divide cm by 100 to convert. Height of 170 cm = 1.70 m.

Step-by-step:

1. Convert your height from cm to meters: divide by 100
2. Square your height in meters: multiply it by itself
3. Divide your weight (kg) by the squared height
4. The result is your BMI

Example: 75 kg, 175 cm

• 175 cm = 1.75 m
• 1.75 × 1.75 = 3.0625
• 75 ÷ 3.0625 = 24.5
• BMI = 24.5 — normal weight

BMI Reference Table — Common Heights and Weights

Weight (kg)	160 cm	165 cm	170 cm	175 cm	180 cm	185 cm
50 kg	19.5	18.4	17.3	16.3	15.4	14.6
55 kg	21.5	20.2	19.0	18.0	17.0	16.1
60 kg	23.4	22.0	20.8	19.6	18.5	17.5
65 kg	25.4	23.9	22.5	21.2	20.1	19.0
70 kg	27.3	25.7	24.2	22.9	21.6	20.5
75 kg	29.3	27.5	26.0	24.5	23.1	21.9
80 kg	31.3	29.4	27.7	26.1	24.7	23.4
85 kg	33.2	31.2	29.4	27.8	26.2	24.8
90 kg	35.2	33.1	31.1	29.4	27.8	26.3
100 kg	39.1	36.7	34.6	32.7	30.9	29.2

Bold cells would indicate the 18.5–24.9 healthy range. Cells below 18.5 represent underweight; 25–29.9 overweight; 30+ obese. The free BMI calculator calculates this precisely for any input values.

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WHO BMI Categories — Metric Reference

BMI	WHO Category	Asian-Specific Category
Below 18.5	Underweight	Underweight
18.5–22.9	Normal weight	Normal weight
23.0–24.9	Normal weight (standard)	Overweight (Asian)
25.0–27.4	Overweight (standard)	Obese I (Asian)
27.5–29.9	Overweight (standard)	Obese I (Asian)
30.0–34.9	Obese Class I	Obese II (Asian)
35.0+	Obese Class II/III	Obese III (Asian)

For people of East Asian, South Asian, or Southeast Asian descent, the WHO recommends using the Asian-specific thresholds. The free BMI calculator uses standard WHO cutoffs — apply the Asian adjustments manually based on the guide linked below if relevant to you.

UK NHS BMI Categories and International Context

The UK National Health Service uses the same WHO BMI categories but with a modification for South Asian, Black African, African-Caribbean, and some other ethnic groups. The NHS recommends that adults from these groups use action thresholds of BMI ≥23 (overweight) and ≥27.5 (obese) — reflecting the same research basis as the WHO Asian-specific recommendations.

The Australian, Canadian, and New Zealand health systems use standard WHO cutoffs for most populations with similar ethnic minority adjustments.

BMI is a consistent calculation globally. The formula is the same whether calculated by the CDC (US), NHS (UK), WHO, or any other body. The categories differ only in where the threshold lines are drawn, not in the underlying math. Enter your metric measurements into the free BMI calculator and apply whichever threshold set is appropriate for your background.

Frequently Asked Questions

How do I calculate BMI in kg and cm?

Convert height from cm to meters (divide by 100). Square the meters value. Divide your weight in kg by the squared height. Example: 72 kg at 175 cm — 1.75 × 1.75 = 3.0625; 72 ÷ 3.0625 = 23.5 BMI (normal weight). Or use a free BMI calculator in metric mode for instant results.

What is a healthy BMI in kg?

BMI is a dimensionless number derived from weight and height — it does not have units like kg. A healthy BMI (18.5–24.9) corresponds to different weights in kg depending on your height. At 170 cm, healthy weight is 53-72 kg. At 180 cm, healthy weight is 60-81 kg. Use the metric BMI table above or a free calculator for your specific height.

Is 25 a good BMI for a woman?

BMI 25 is at the boundary between normal weight (18.5-24.9) and overweight (25+) by standard WHO cutoffs. For most women of European descent, a BMI just at or slightly above 25 carries minimal elevated risk. For women of Asian descent, BMI 23-25 is already in the overweight range by Asian-specific guidelines. The context — waist circumference, blood markers, and fitness level — matters as much as the number itself.