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Waist-to-height ratio calculator

Divide your waist by your height. The NHS advice is simple: keep your waist to less than half your height.

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Height

I’m cm tall, and my waist is cm.

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Measure midway between the bottom of your ribs and the top of your hips, breathing out naturally, not pulled in.

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Enter your waist measurement and height to see your waist-to-height ratio.

What does my ratio mean?

The NHS advice is to keep your waist size to less than half your height[NHS]. That is a ratio below 0.5. Someone 170 cm tall should aim to keep their waist under 85 cm.

What this measures that BMI cannot is where fat is stored. Fat around the middle, around the organs rather than under the skin, is more strongly associated with cardiovascular risk and type 2 diabetes than overall weight is.

The NHS suggests using waist-to-height ratio alongside BMI if your BMI is under 35[NHS]. Above that, the additional information it adds is limited.

Only one threshold, deliberately

Some calculators show four or five bands with labels like "very high risk". The NHS publishes one threshold, half your height, so that is what we show. We would rather give you one figure we can cite than several we cannot.

How to measure and calculate

ratio = waist ÷ height (both in the same unit)
Waist-to-height ratio

Measuring your waist correctly

  1. Find the bottom of your ribs and the top of your hips.
  2. Wrap a tape measure around your middle, midway between those two points; for most people this is roughly level with the belly button.
  3. Breathe out naturally, and do not pull the tape tight or hold your stomach in.
  4. Take the measurement against skin or thin clothing.

Measuring in the same place each time matters more than measuring in exactly the right place. A consistent method makes the change over time meaningful, which is usually more useful than any single reading.

Limitations

  • Waist measurement is easy to get wrong, and small differences in tape position change the result.
  • It is one signal among several, not a diagnosis.
  • It is not appropriate during pregnancy.
  • The single 0.5 threshold is a simplification: risk does not switch on at a precise number.

If your ratio is above 0.5, it is worth mentioning at your next GP appointment rather than acting on alone. It is a prompt for a conversation, not a conclusion.

Related calculators

Frequently asked questions

What is a healthy waist-to-height ratio?

Below 0.5, meaning your waist is less than half your height. This is the threshold the NHS uses, and it has the advantage of applying regardless of your height, without needing a chart.

Is waist-to-height ratio better than BMI?

It is not better so much as different. BMI reflects overall weight relative to height; waist-to-height reflects where weight is carried. The NHS suggests using both where BMI is under 35, because together they say more than either does alone.

Where exactly should I measure my waist?

Midway between the bottom of your ribs and the top of your hips, which for most people sits at about the level of the belly button. Breathe out naturally before reading the tape, and do not pull it tight.

Sources

  1. Obesity: diagnosis, NHS
  2. Obesity, NHS
  3. Overweight and obesity in adults, NHS

Important information

The calculators on this site provide general information and estimates. They are not medical advice and they do not diagnose any condition.

Everyone is different, and individual energy needs vary for reasons these equations cannot capture. If you have a health condition, take medication, are pregnant or breastfeeding, or have any concerns about your weight, speak to your GP, pharmacist or a registered dietitian.