❤️ Health · BMI

How to Calculate
BMI

Calculate your Body Mass Index in metric or imperial units. Understand what your BMI means and see the full category chart.

BMI Formulas

Metric (kg / cm)
BMI = kg ÷ m²
Divide weight in kg by height in metres squared
Imperial (lb / in)
BMI = 703 × lb ÷ in²
Multiply 703 by weight in pounds, divide by height in inches squared
💡 Example (metric): 70 kg, 1.75 m → BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 — Normal weight ✅

BMI Calculator

Your BMI
22.9
Normal weight ✅
Healthy BMI range: 18.5 – 24.9
1618.5253040
Your BMI
22.7
Normal weight ✅
Healthy BMI range: 18.5 – 24.9
1618.5253040

BMI Categories

CategoryBMI RangeHealth Risk
UnderweightBelow 18.5Malnutrition, osteoporosis risk
Normal weight18.5 – 24.9Lowest health risk
Overweight25.0 – 29.9Moderate increased risk
Obese Class I30.0 – 34.9High health risk
Obese Class II35.0 – 39.9Very high health risk
Obese Class III40.0 and aboveExtremely high health risk

Step-by-Step Guide

1

Measure your height and weight

Use consistent units. Metric: kilograms and centimetres. Imperial: pounds and inches (12 in = 1 ft).

2

Convert height to metres (metric)

Divide cm by 100. Example: 175 cm ÷ 100 = 1.75 m. Then square it: 1.75 × 1.75 = 3.0625

3

Apply the formula

Metric: 70 ÷ 3.0625 = 22.9. Imperial: 703 × 154 ÷ (69 × 69) = 22.7

4

Find your category

Below 18.5 = underweight. 18.5–24.9 = normal. 25–29.9 = overweight. 30+ = obese.

Worked Examples

Underweight

50 kg, 170 cm
50 ÷ (1.70)² = 50 ÷ 2.89
BMI = 17.3 ⚠️

Normal Weight

68 kg, 175 cm
68 ÷ (1.75)² = 68 ÷ 3.06
BMI = 22.2 ✅

Overweight

90 kg, 175 cm
90 ÷ (1.75)² = 90 ÷ 3.06
BMI = 29.4 ⚠️

Imperial

180 lb, 5′10″ (70in)
703 × 180 ÷ (70)²
BMI = 25.8 📊

More Health Calculators

🔥
Calorie Deficit
Lose weight safely
📏
Body Fat %
More accurate than BMI
🥗
Macros
Protein, carbs & fat
⚖️
Maintenance Calories
TDEE calculator
💓
Heart Rate Zones
Max & target HR
💵
Net Income
Take-home pay

Frequently Asked Questions

What is a healthy BMI for adults? ▾
A BMI between 18.5 and 24.9 is considered healthy for adults. This is the range associated with the lowest risk of weight-related health conditions.
Is BMI accurate for athletes and muscular people? ▾
No — BMI doesn't distinguish between fat and muscle. A muscular athlete may have a BMI in the "overweight" range despite having very low body fat. In these cases, body fat percentage measurement is more meaningful.
Does BMI differ for men and women? ▾
The standard BMI formula and categories are the same for men and women. However, women naturally carry more body fat than men at the same BMI, which some researchers argue makes the categories imprecise.
What BMI is considered obese? ▾
A BMI of 30 or above is classified as obese. Class I is 30–34.9, Class II is 35–39.9, and Class III (severe obesity) is 40 and above.
How can I lower my BMI? ▾
BMI decreases when you reduce body fat through a combination of calorie deficit (consuming fewer calories than you burn) and regular physical activity. Losing 0.5–1 kg per week is considered a healthy, sustainable rate.