What is BMI?

BMI is a number that indicates whether your weight is healthy for your height. It’s not perfect (it doesn’t account for muscle vs. fat), but it’s a good starting point to understand your health. Here’s what the numbers mean:

Under 18.5: Underweight

18.5 – 24.9: Normal weight

25 – 29.9: Overweight

30 and above: Obesity

How to Use the BMI Calculator

BMI, or Body Mass Index, is a simple number that gives you a quick snapshot of whether your weight is in a healthy range for your height. It's not perfect it doesn't account for muscle mass or body composition, but it's a widely used screening tool and a useful starting point.

Step 1: Choose your unit system. Click "Metric" if you know your measurements in kilograms and centimeters. Click "US" if you work in pounds and inches.

Step 2: Enter your age and gender. These don't change your BMI number itself, but they personalise the health insights shown in the results.

Step 3: Enter your weight and height. Double-check you're using the right units — it's easy to accidentally enter 175 lbs when you mean 175 cm.

Step 4: Click Calculate BMI. Your result appears instantly.

Reading your result: The calculator shows your BMI number, your category, and a visual bar showing where you fall across the four standard ranges. Underweight is below 18.5. Normal weight is 18.5 to 24.9. Overweight is 25 to 29.9. Obesity is 30 and above.

You'll also get personalised health tips based on your category — simple, actionable suggestions rather than generic advice.

One important note: BMI is a screening tool, not a diagnosis. Athletes and very muscular people often show a high BMI despite being extremely healthy. Always talk to a healthcare professional before making medical decisions based on any calculator.

Other Calculators You Might Find Useful:

Calories Burned Calculator — Find out how many calories you burned during your run or workout

Target Heart Rate Calculator — Calculate your ideal heart rate zones for every training intensity

VO2 Max Calculator — Estimate your aerobic fitness level with 5 proven test methods

Body Fat Calculator — Measure your body composition beyond just weight

Pace Calculator — Calculate your running pace, finish time or distance