Last updated: May 2026

BMI Calculator

Quick answer: An 80 kg adult who is 180 cm (1.80 m) tall has a BMI of 24.7 — Normal weight on the WHO scale. Formula: BMI = Weight (kg) ÷ Height (m)².

About this calculator

The BMI calculator computes body mass index using the formula BMI = Weight (kg) ÷ Height (m)², converting imperial inputs to metric first when needed. It is a population-level screening tool — not a clinical diagnosis. BMI is commonly used to assess GLP-1 eligibility — if you are calculating semaglutide or tirzepatide draw volumes, use the semaglutide dosage calculator. Your result appears instantly alongside the WHO reference category. Free, no login.

How to use this calculator

Select your preferred unit system — metric or imperial — using the toggle at the top of the calculator. Enter your height and weight. BMI updates immediately as you type.

The result includes your numeric BMI and the corresponding WHO category (Underweight, Normal weight, Overweight, or Obese). No data is stored or sent anywhere — the calculation happens entirely in your browser.

Worked examples

Metric example

Weight: 80 kg · Height: 180 cm (1.80 m)

BMI = 80 ÷ (1.80 × 1.80) = 80 ÷ 3.24

BMI = 24.7 — Normal weight

Imperial example

Weight: 176 lb · Height: 5 ft 11 in

Converted: 79.8 kg · 180.3 cm → BMI = 79.8 ÷ 3.25

BMI = 24.5 — Normal weight

WHO BMI categories (adults)

BMI range	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obese (Class I)
35.0 – 39.9	Obese (Class II)
40.0 and above	Obese (Class III)

What BMI does and does not measure

BMI is a population-level screening tool. It is calculated from height and weight only, so it cannot distinguish between fat mass and muscle mass. A person with significant muscle (such as someone doing resistance training or on TRT) may have a BMI in the "overweight" range while carrying very little excess body fat.

BMI also does not account for fat distribution. Two people with the same BMI can have very different risk profiles depending on where their body fat is stored. Use BMI as a rough indicator, not a complete picture of body composition or health.

Frequently asked questions

What is the BMI formula?

BMI = weight in kilograms ÷ (height in metres)². In imperial: BMI = (weight in pounds × 703) ÷ (height in inches)². Both produce the same result when units are consistent.

Is BMI accurate for muscular people?

No — BMI does not account for the difference between fat and muscle. A muscular person may score in the overweight range despite having low body fat. For people doing resistance training or on Testosterone (TRT), BMI is a less reliable indicator than body fat percentage or waist circumference.

Does BMI apply the same way for everyone?

The standard WHO thresholds were established using primarily Western European population data. Some health authorities recommend lower cutoffs for East Asian populations, where metabolic risk occurs at lower BMI values. Discuss with your doctor what the right reference range is for you.

What BMI qualifies for semaglutide or tirzepatide?

In most countries, GLP-1 receptor agonists like semaglutide (Wegovy/Ozempic) and tirzepatide (Mounjaro/Zepbound) are prescribed for adults with a BMI of 30 or higher, or a BMI of 27 or higher alongside a weight-related condition such as type 2 diabetes, hypertension, or high cholesterol. Eligibility criteria vary by country and prescriber — use this BMI calculator to check your current BMI, then discuss prescribing criteria with your doctor.

How much weight do I need to lose to change my BMI category?

It depends on your height. For someone 175 cm tall, each kilogram of weight change shifts BMI by roughly 0.33 points — so dropping a full category from 30 to 25 requires losing roughly 15 kg. Enter your target BMI and height in the calculator above to see your target weight.

Other calculators

Testosterone (TRT) Dosage Peptide Reconstitution Peptide Dosage Free Testosterone Index Semaglutide Tirzepatide Retatrutide BPC-157 BPC-157 + TB-500 Blend

Related guides

How this is calculated

BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²); the categories follow the WHO thresholds shown above. It runs entirely in your browser — nothing is stored — and is a screening figure, not medical advice.