BMI Calculator
Calculate body mass index from height and weight with a healthy range.
Written by Anil Gautam · Updated
How is BMI calculated?
BMI is weight in kilograms divided by the square of height in metres. At 170 cm and 70 kg: 70 ÷ (1.7 × 1.7) = 70 ÷ 2.89 = 24.22, which falls in the healthy weight band. Other units are converted first: inches are multiplied by 0.0254 and feet by 0.3048 to get metres, and pounds by 0.45359237 to get kilograms.
The bands are below 18.5 for underweight, 18.5 up to 25 for healthy weight, 25 up to 30 for overweight, and 30 or more for the obesity range. Your healthy weight range is 18.5 and 24.9 multiplied by your height in metres squared, shown in the weight unit you picked: 53.46 to 71.96 kg at 170 cm. At 175 cm and 80 kg, BMI is 26.12, in the overweight band, and the healthy range tops out at 76.26 kg.
Why is my BMI off when I enter height in feet?
The feet option takes decimal feet. A height of 5 feet 6 inches is 5.5 feet, and typing 5.6 means 5 feet 7.2 inches, because 0.6 of a foot is 7.2 inches. At 70 kg, 5.5 feet gives a BMI of 24.91 and 5.6 feet gives 24.03. Pick inch and enter 66, or convert first with Height Converter.
Changing a unit menu does not convert the number already in the box. Switch height from cm to inch while 170 is entered and the calculator reads 170 inches, giving a BMI of 3.75 with the default 70 kg. Retype the value after changing units.
What can BMI not tell you?
BMI uses only height and weight, so it cannot separate muscle from fat or show where fat is stored, and a muscular person can read as overweight. The bands are for adults; children and teenagers are assessed on age and sex percentile charts. Guidelines used in India and some other Asian countries start the overweight band at 23, so a reading of 24 can count as overweight there.
Read the number as a screening figure. If yours falls outside the healthy band, a doctor can interpret it alongside your waist size and other measurements. For a daily calorie estimate at your current weight, use BMR & TDEE Calculator.