BMI + Waist Comparison
Enter your height, weight and waist to see your BMI and waist-to-height ratio side by side. For adults.
- Your waist
- Half your height
- Difference
These are general screening measures, not a diagnosis. BMI categories (such as "healthy weight") can depend on factors like ethnic background, so use the NHS BMI calculator for your category. Not suitable if you are pregnant or have an eating disorder, or for children. Nothing you enter is stored or sent anywhere.
What your two results mean
This tool shows two measurements side by side. They answer different questions, so neither one is a complete picture on its own.
| BMI | Waist-to-height ratio | |
|---|---|---|
| How it is calculated | Weight in kilograms divided by height in metres squared | Waist circumference divided by height, in the same units |
| What it compares | Your weight with your height | Your waist size with your height |
| What it does not tell you | How much of your weight is muscle or fat, or where fat is stored | Your overall weight or body composition |
The NIDDK explains that BMI does not directly measure body fat, and that where your body stores fat matters, especially around the abdomen. It also notes that a very muscular person may have a high BMI without carrying much body fat.
Why we show the BMI number but no category
This tool shows your BMI as a number only. The NHS BMI calculator also asks about your ethnic background so that its advice is more accurate, which means the category that fits you can differ from a standard chart. To see your category, use the NHS BMI calculator linked in the sources below.
How to measure your waist
- Stand upright and relaxed, with your stomach unclenched.
- Find the point halfway between your lowest rib and the top of your hip bone.
- Wrap a soft tape measure around your bare waist at that point, keeping it level all the way around.
- Breathe out normally, then read the measurement. The tape should be snug but not pressing into your skin.
For the full guide, see our Waist-to-Height Ratio Calculator page.
Limitations and who should not use this tool
This is a general educational tool and cannot diagnose any condition. Following the NHS’s guidance for its own calculators, do not use it if you:
- are under 18 (the adult BMI method is not suitable, and children’s BMI is assessed differently)
- are pregnant
- have been diagnosed with an eating disorder, or think you may have one
- have a condition that affects your height
The NHS also says its waist-to-height ratio calculator is not intended for adults with a BMI over 35. Measurement errors matter too: a tape in the wrong place or pulled too tight changes your waist result. If you are worried about your weight or waist size, contact your local pharmacist or doctor.
Frequently asked questions
What is the difference between BMI and waist-to-height ratio?
BMI compares your weight with your height. Waist-to-height ratio compares your waist size with your height. BMI does not directly measure body fat or show where fat is stored, so the two are most useful together.
Which one is better?
Neither is complete on its own. They measure different things, so it is more useful to look at both, alongside your habits and advice from a healthcare professional.
Why doesn’t the tool tell me if my BMI is “healthy” or not?
BMI categories can depend on factors such as ethnic background, which the NHS BMI calculator takes into account. We show the number only, and point you to the NHS calculator for your category.
What waist-to-height ratio should I aim for?
The NHS advises trying to keep your waist size to less than half your height, which is a ratio below 0.5. It is a general guide, not a personal target.
Does the tool store my numbers?
No. The calculation runs in your browser. Nothing you enter is saved or sent anywhere.
Sources
- NHS: Calculate your body mass index (BMI) for adults
- NHS: Calculate your waist-to-height ratio
- NIDDK, National Institutes of Health: Am I at a healthy weight?
More Tools: Waist-to-Height Ratio Calculator
Last reviewed: October 13, 2026. This page provides general educational information and does not give medical advice. Talk to a qualified healthcare professional about your own health.