Measuring your body shape

The four numbers

Take them over light clothing or none, standing normally, and let the tape sit level all the way round rather than riding up at the back. Breathe out but do not hold it in. The tape should touch without denting.

Two of these do more work than the other two. The waist is in every threshold below, and the hip is what makes the difference between a reading that can see a waist and one that cannot. Without a hip measurement the classifier falls back to a shoulder-and-chest reading, which cannot reach the two shapes defined by hip width at all.

• Shoulder: straight across the back from the outer point of one shoulder to the other. This is the one no other measurement substitutes for, and the one a photo reads better than a tape.
• Chest or bust: the fullest part, tape level, arms down.
• Waist: the narrowest part of the torso, which is usually just above the navel and is not where your trousers sit.
• Hip: the fullest part of the seat, usually 18 to 20cm below the waist, feet together.

The differences that decide it

The classifier does not read your measurements. It reads the differences between them, which is why two people of very different sizes get the same shape and the same advice. Every number below was found by holding the other measurements still and moving one until the label changed, so it is the classifier's own line rather than a number quoted at it.

The published thresholds behind these are stated in inches and have no derivation: they were reverse-engineered from verbal descriptions of shapes rather than fitted to bodies. They are used anyway, because a documented arbitrary line beats an undocumented one, and because the advice underneath is graded by how firmly you sit inside your label rather than argued at full volume from the label alone.

• Bust minus waist of 22.9cm or more, with the hip level with the bust, reads as a defined waist.
• Hip minus waist of 25.4cm does the same job when the bust is not the thing defining it.
• Hip 9.2cm or more past the bust puts the width low; bust 9.2cm or more past the hip puts it high. Anything short of that and the two count as level.
• Waist at or above the bust reads as weight carried centrally, whatever the rest of the numbers say.
• With no hip measurement: shoulder-to-waist ratio at 1.35 or above reads as a balanced build, 1.5 and above with a chest-minus-waist drop of at least 18cm reads as broad-shouldered, and 1.15 or below puts the width at the waist.

Two centimetres decide more than they should

Measure yourself twice on the same afternoon and you will get numbers two centimetres apart. That matters here more than it should: in a study of 1,679 women, up to 40% changed shape category depending only on which measurement-placement protocol was used, and that disagreement is larger than the gap between many of the thresholds above.

So the honest way to use this page is as a range rather than a verdict. If moving your waist by two centimetres in either direction would move you into a different shape, you are a borderline case, and the useful thing to do is read both pages and take what they agree on. That is also what the product does: it perturbs your measurements, sees how often the label survives, and argues more quietly when it does not.

Where each answer goes

Seven shapes, each with its own page: the rule for it in one sentence, and every common garment scored against it by the same table the product uses on real products.

The names on the left are what a person says. The names on the right are what the engine calls them, and they are only there so the two halves of the site can be matched up.

• A straight up-and-down build, which the engine calls a rectangle.
• Narrow shoulders and wider hips, which the engine calls a triangle.
• Broad shoulders, which the engine calls an inverted triangle.
• An average, balanced build, which the engine calls a trapezoid.
• A fuller middle, which the engine calls an oval.
• A defined waist, which the engine calls an hourglass.
• Wider hips with a defined waist, which the engine calls a spoon.