BMI Calculator
Calculate your Body Mass Index instantly. Enter your height and weight in imperial or metric units to see your BMI score, weight category, and the healthy weight range for your height.
e.g. 5 ft 9 in
e.g. 154 lbs
Your BMI
A BMI between 18.5 and 24.9 is within the healthy range for most adults. Maintaining this range through a balanced diet and regular physical activity supports long-term wellbeing.
Healthy weight for your height
125 – 169 lbs
BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, age, sex, or ethnicity. Consult a qualified healthcare professional for a personalised health assessment.
How to Use This BMI Calculator
Using this calculator takes less than a minute. Follow these steps:
- Choose your unit system — select Imperial (feet, inches, pounds) or Metric (centimetres, kilograms) using the toggle at the top of the calculator.
- Enter your height — in centimetres for metric, or feet and inches separately for imperial.
- Enter your weight — in kilograms for metric or pounds for imperial.
- Read your result instantly — your BMI value, weight category, visual scale position, and healthy weight range for your height are all displayed as you type.
No button press is needed — results update in real time. You can switch between Imperial and Metric at any time without losing your inputs.
BMI Formula & Categories
Metric Formula
BMI = weight (kg) ÷ height (m)²Example: 70 kg ÷ (1.75 m)² = 22.9
Imperial Formula
BMI = 703 × weight (lbs) ÷ height (in)²Example: 703 × 154 lbs ÷ (69 in)² = 22.7
WHO BMI Categories
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
The 703 multiplier in the imperial formula converts lbs/in² to the equivalent kg/m² scale, ensuring imperial and metric BMI values are directly comparable.
Frequently Asked Questions
BMI, or Body Mass Index, is a numerical value calculated from a person's height and weight. It provides a simple screening tool to categorize a person as underweight, normal weight, overweight, or obese. It is widely used by healthcare professionals as a quick initial assessment.
In metric units: BMI = weight(kg) ÷ height(m)². In imperial units: BMI = 703 × weight(lbs) ÷ height(inches)². For example, a person weighing 70 kg at 1.75 m tall has a BMI of 70 ÷ (1.75²) = 22.9.
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. These thresholds are general guidelines and may not apply equally to all individuals or ethnic groups.
BMI is a useful population-level screening tool but has limitations. It does not directly measure body fat or account for muscle mass, bone density, age, sex, or ethnicity. Athletes may have a high BMI due to muscle mass without excess fat. Always consult a healthcare professional for a comprehensive health assessment.
The standard BMI formula and categories are the same for both men and women. However, women typically have a higher body fat percentage than men at the same BMI. Some researchers advocate for sex-specific BMI cutoffs, but the WHO and CDC currently use the same thresholds for all adults.
In imperial units, BMI = 703 × weight(lbs) ÷ height(inches)². The 703 conversion factor adjusts the result so imperial BMI values match the metric standard. For example, a person who is 5 ft 9 in (69 inches) and weighs 154 lbs has a BMI of 703 × 154 ÷ 69² = 22.7.
Related Calculators
Calorie Deficit Calculator
Find your TDEE and daily calorie deficit for weight loss.
Health Insurance Calculator
Estimate ACA marketplace premiums and your Premium Tax Credit.
Life Insurance Calculator
Estimate how much life insurance you need and compare premiums.