Body Type Calculator: How Your Shape Is Decided

The categories sound vague until you see the arithmetic behind them. Every body type calculator is running two or three ratio tests in a fixed order, and once you know what they are, the result stops being mysterious and starts being checkable.

What the three numbers get compared against

The tests are roughly these. If bust and hips are within about 5% of each other and the waist is at least 25% smaller than both, that is an hourglass. If hips beat bust by more than about 5%, it is a pear or triangle. If bust beats hips by that margin, inverted triangle. If the waist is less than about 25% below the larger of bust and hips, rectangle. Apple describes a waist that measures close to or above the bust.

Run the example: 34, 27, 37. Hips are 3 inches wider than the bust, which is 8.8%, over the 5% threshold, so the shape is a pear. The waist is 10 inches below the hips, which is 27%, so it is a defined pear rather than a straight one.

Where the tape goes

Bust at the fullest point, tape level all the way round and not pulled tight. Waist at the narrowest point, which for most people is roughly an inch above the navel and not where trousers sit. Hips at the widest point, usually 7 to 9 inches below the waist, which often means lower than people expect. Wear thin clothing or none, and breathe out normally rather than holding it.

Borderline results flip easily

Consider a bust of 38, a waist of 28 and hips of 38.5. Bust and hips are 1.3% apart, so that test passes. The waist sits 10.5 inches below the hips, which is 27%, and 10 inches below the bust, which is 26%. Both clear the 25% mark, so the answer is hourglass. Now take that same waist at the navel rather than the narrowest point and record 30. The gap to the hips drops to 8.5 inches, or 22%, and the calculator returns rectangle instead.

Two inches of tape placement changed the category. If your numbers sit near a boundary, measure three times on different days and take the middle reading. And treat the label as a description of proportions, not a verdict. A shape category tells you nothing about health, which is what body fat percentage against BMI is for.

Using the calculator

You need a flexible tape measure and three numbers. Enter bust, waist and hips in inches or centimetres, using one unit throughout: 34, 27, 37 in inches is 86, 69, 94 in centimetres. Some versions also ask for shoulder width, which separates inverted triangle from rectangle more reliably than bust alone. If you have measured recently for a bra fitting, note that the band measurement sits under the bust and is not the same number the calculator wants.

Measure in the morning if you can. Bloating late in the day can add an inch at the waist, which is enough to move you across a threshold.

Common questions

Can your body type change? The ratios shift with weight change, pregnancy, and age. Where you gain and lose is largely set by genetics, so someone who gains at the hips will usually stay a pear at any weight, but the numbers themselves move enough to cross a category line.

Does body shape say anything about health? The shape label does not, but waist size does. A large waist relative to height is the part clinicians care about, which is why waist-to-height and waist-to-hip ratios exist as separate measures. An apple result is worth following up with one of those.

Do men have body types too? Yes, usually described as triangle, inverted triangle, rectangle or oval, based on shoulders, chest and waist rather than bust and hips. The same calculator works if you enter chest in place of bust, though the thresholds were built around a different distribution.

Which measurement do people get wrong most? The waist, by a wide margin. Measuring at the navel or at the trouser line instead of the narrowest point commonly adds one to two inches, and that is exactly the amount that changes the answer.