tigtools

BMI Calculator

Enter your height and weight to calculate your body mass index (BMI). For adults aged 18 and over. BMI is a screening number, not a diagnosis.

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Units

Enter your height and weight to see your BMI.

For adults aged 18 and over. BMI does not apply to children and teenagers (who need age- and sex-specific growth charts), to pregnancy, or reliably to athletes and very muscular people. It does not measure body fat or health and is not medical advice: talk to a doctor or another health professional about your weight.

How to use it

  1. Choose metric (kg and cm) or imperial (pounds, feet and inches).
  2. Enter your weight and your height.
  3. Read your BMI, its WHO category, and the weight range that corresponds to a BMI of 18.5 to 24.9 at your height.

How it works

Body mass index is weight divided by height squared: BMI = kg ÷ m². In imperial units the same formula is BMI = 703 × lb ÷ in²; this calculator converts pounds and inches to kilograms and metres with the exact factors (1 lb = 0.45359237 kg, 1 in = 2.54 cm) and then applies the metric formula.

The World Health Organization classifies adult BMI as: underweight below 18.5; normal weight 18.5 to 24.9; pre-obesity (overweight) 25.0 to 29.9; obesity class I 30.0 to 34.9; class II 35.0 to 39.9; and class III 40 and above. The BMI is shown to one decimal and the category is based on that shown value. The healthy-weight range is the weight that gives a BMI of 18.5 to 24.9 at your height.

BMI is a quick screening measure for populations and a starting point for a conversation with a health professional. It does not distinguish fat from muscle, bone or water, and it does not show where fat is stored. It is not valid for children and teenagers, during pregnancy, and is less reliable for athletes, older adults and some ethnic groups, for which some health bodies use lower cut-off points. It is not a diagnosis and not medical advice.

Examples

Metric

70 kg and 175 cm: 70 ÷ 1.75² = 70 ÷ 3.0625 = 22.9, which is in the normal weight range. At 175 cm, a BMI of 18.5–24.9 corresponds to about 56.7–76.3 kg.

Imperial

154 lb at 5 ft 9 in (69 in): 703 × 154 ÷ 69² = 22.7. The calculator gets the same result by converting to 69.9 kg and 1.7526 m.

Frequently asked questions

Can I use this BMI calculator for my child?

No. Children's and teenagers' BMI must be compared with growth charts for their exact age and sex (BMI-for-age percentiles). The adult categories here do not apply under 18.

Why can a muscular person have an overweight BMI?

BMI only uses height and weight. Muscle is dense, so athletes can have a high BMI with little body fat. Waist measurement or body composition tests give more information.

Is the healthy BMI range the same for everyone?

The WHO ranges are the international standard for adults, but some health bodies use lower cut-offs for people of Asian descent, and older adults may be advised differently. Ask a health professional which applies to you.

What is the BMI formula in pounds and inches?

BMI = 703 × weight in pounds ÷ (height in inches)². The factor 703 comes from converting pounds to kilograms and inches to metres.

Privacy

Height and weight are processed only in your browser. They are not sent, stored or included in analytics.