BMI Calculator (Body Mass Index)

This calculator uses the standard WHO formula:

BMI = weight (kg) / height² (m²)

Since you enter your height in centimeters, the first step is converting it to meters by dividing by 100.

Worked example. A 6-foot adult (183 cm) weighing 203 pounds (92 kg):

1. Height in meters: 183 / 100 = 1.83 m 2. Height squared: 1.83 × 1.83 = 3.3489 m² 3. BMI: 92 / 3.3489 = 27.5

A BMI of 27.5 falls in the overweight category (25.0–29.9).

Healthy weight range. The calculator also runs the formula in reverse to show which weights would put you in the normal range for your height:

• Minimum healthy weight = 18.5 × height² = 18.5 × 3.3489 = 62.0 kg (about 137 lb)
• Maximum healthy weight = 24.9 × height² = 24.9 × 3.3489 = 83.4 kg (about 184 lb)

So a 6-foot adult stays in the normal BMI range between roughly 137 and 184 pounds. If you prefer to work entirely in imperial units, the equivalent formula is BMI = 703 × weight (lb) / height² (in²) — for our example, 703 × 203 / 72² = 27.5, the same result.

1. Enter your weight in kilograms. If you only know pounds, divide by 2.2046 — for example, 180 lb ÷ 2.2046 = 81.6 kg. Decimals are fine. 2. Enter your height in centimeters. If you know it in feet and inches, convert to total inches and multiply by 2.54 — for example, 5'10" is 70 inches × 2.54 = 178 cm. 3. Read the three results. Your BMI to one decimal place, plus the minimum and maximum weight that would put you in the normal range (18.5–24.9) for your height.

To interpret your score, check the WHO category table in the context section below. One practical tip: a single reading matters less than the trend. Weighing yourself under similar conditions — same time of day, similar clothing — and recalculating monthly tells you far more than day-to-day numbers, which can swing a couple of pounds on water weight alone.

The table below shows BMI for four typical profiles, calculated with the WHO formula:

Two takeaways worth noticing:

• The 38-year-old at 203 lb sits about 19 lb above his healthy maximum of 83.4 kg (184 lb). A modest, sustained change is enough to move categories.
• For the 45-year-old, the healthy range at 178 cm runs from 58.6 to 78.9 kg (129 to 174 lb). Losing one pound a week — a commonly cited sustainable pace — would take him a bit over a year to reach the top of that range.

The WHO classifies adult BMI into four main categories:

Obesity is further divided into class 1 (30–34.9), class 2 (35–39.9) and class 3 (40 and above).

In the United States, CDC surveys show that roughly four in ten adults have obesity, which is why BMI screening is a routine part of checkups and why clinicians track it over time.

Known limitations of BMI:

• It cannot tell muscle from fat. A 220-pound linebacker and a sedentary person of the same height and weight get identical scores.
• It says nothing about where fat is stored, yet abdominal fat carries the strongest cardiovascular risk — which is why clinicians pair BMI with waist circumference.
• It applies differently, or not at all, to children and teens (who use age- and sex-specific percentiles), pregnant women, and adults over 65.

This calculator is for educational purposes only — it is not medical advice and does not replace an evaluation by a healthcare professional.

It is the measure used by the CDC and the World Health Organization as a first-line check of weight status. This calculator returns your BMI instantly and also shows the minimum and maximum weight that would keep you inside the healthy range (18.5 to 24.9) for your height. For example, someone who is 6 feet tall (1.83 m) has a healthy range of roughly 62.0 to 83.4 kg — about 137 to 184 pounds. Keep in mind that BMI is a screening tool, not a diagnosis: it cannot tell muscle from fat, so a 200-pound athlete and a sedentary person of the same height and weight get the same score. Use it together with other markers such as waist circumference.