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BMI Calculator

Updated · By the CalculatorDash editorial team · How we check our maths

Quick answer

BMI = weight (kg) ÷ height (m)². For a person 1.75 m tall weighing 70 kg, BMI is about 22.9, inside the healthy range of 18.5–24.9, which for that height is roughly 56.7–76.3 kg. In imperial units, BMI = 703 × weight (lb) ÷ height (in)².

BMI

Your BMI

22.9

Under 18.5 underweight · 18.5–24.9 healthy · 25–29.9 overweight · 30+ obesity (WHO adult categories).

Healthy weight from
56.7
Healthy weight up to
76.3

BMI is a screening measure, not a diagnosis. It doesn't distinguish muscle from fat and isn't suitable for children or pregnancy.

How this calculator works

Body mass index compares weight with height to give a quick screening number. The World Health Organization classes adult BMI under 18.5 as underweight, 18.5–24.9 as a healthy weight, 25–29.9 as overweight and 30 or more as obesity.

BMI is useful for populations and as a starting point, but it has limits: very muscular people can score as overweight, and it says nothing about where fat is carried. Some health bodies use lower thresholds for people of South Asian, Chinese and other Asian heritage. Waist measurement and a conversation with a doctor give a fuller picture.

The formula

Metric
BMI = weight in kg ÷ (height in m)²
Imperial
BMI = 703 × weight in lb ÷ (height in inches)²
Healthy range
18.5 × height² to 24.9 × height² (in kg with height in m)

Worked example

70 kg at 1.75 m: 70 ÷ 1.75² = 70 ÷ 3.0625 = 22.9. The healthy range for 1.75 m is 18.5 × 3.0625 = 56.7 kg to 24.9 × 3.0625 = 76.3 kg. In imperial units, 160 lb at 68 inches gives 703 × 160 ÷ 68² = 24.3.

Tips

  1. 01Weigh yourself at the same time of day for consistent readings.
  2. 02Pair BMI with waist size; a waist over half your height is a common warning sign.
  3. 03Talk to a doctor before making big changes to diet or exercise.

Frequently asked questions

What is a healthy BMI?

For most adults, 18.5 to 24.9. Some guidelines use lower cut-offs for people of Asian heritage.

Is BMI accurate for athletes?

Not very. Muscle is dense, so muscular people can have a high BMI without excess fat.

How do I calculate BMI in pounds and inches?

Multiply weight in pounds by 703, then divide by height in inches squared.

Can children use this BMI calculator?

No. Children's BMI is interpreted with age- and sex-specific percentiles. Use a paediatric calculator.