Waist-to-Height Ratio (WHtR)

What the Waist-to-Height Ratio Calculator Does

This calculator works out your waist-to-height ratio (WHtR), a quick screen for central (abdominal) fat. It divides your waist circumference by your height, giving a single number that flags whether you may be carrying excess fat around your middle.

WHtR is useful for adults of any height or build because it adjusts your waist measurement for how tall you are. It is often used alongside or instead of BMI, since BMI cannot tell where fat is stored. The calculator is a screening aid, not a diagnosis.

How the Waist to Height Ratio Is Calculated

The formula is simple and uses the same unit for both measurements so they cancel out:

ratio = waist circumference / height

Measure both in centimetres (or both in inches) — the ratio is the same either way. The widely cited guideline is to keep your waist less than half your height, so aim for a ratio below 0.5.

• Below 0.4: may indicate too little weight
• 0.4 to 0.49: healthy central-fat range
• 0.5 to 0.59: increased risk, consider taking action
• 0.6 and above: substantially increased risk

Worked Example With Real Numbers

Suppose an adult is 170 cm tall with a waist of 80 cm. Divide 80 by 170 to get a ratio of 0.47.

Because 0.47 is below 0.5, this falls in the healthy 0.4 to 0.49 band — the waist is less than half the person's height. If the same person's waist grew to 90 cm, the ratio would be 90 / 170 = 0.53, crossing into the increased-risk range.

The math is identical in inches: a 67-inch-tall person with a 31.5-inch waist gets 31.5 / 67 = 0.47, the same result.

How to Measure Your Waist Correctly

An accurate ratio depends entirely on an accurate waist measurement. Most of the inconsistency people see comes from measuring in the wrong place or at the wrong moment.

• Measure midway between the lowest rib and the top of the hip bone, roughly level with the navel
• Stand up straight and breathe out normally before reading the tape — do not suck in
• Keep the tape snug and horizontal, not pulled tight enough to compress the skin
• Measure on bare skin or over very thin clothing, not over a belt or bulky layers

Common Mistakes and Factors That Affect the Result

The most frequent errors are mixing units (waist in inches, height in centimetres) and measuring over clothing, both of which throw the ratio off. Always use the same unit for both numbers.

Keep in mind the 0.5 threshold is a general adult guideline. Pregnancy changes waist size for reasons unrelated to fat, and children use age-adjusted charts rather than the flat 0.5 cutoff. Body composition also matters — a very muscular midsection can raise the number without the same risk.

Use WHtR as one signal among several. If your result is 0.5 or higher, or you are unsure how to interpret it, discuss it with a healthcare professional rather than relying on the calculator alone.