How we classify body shape
Every rule the calculator applies, the thresholds it uses, the order it runs them in, and the cases it gets wrong. Published so you can disagree with it.
The four measurements
The method uses bust, waist, hips and shoulders. Most calculators ask for three and drop the shoulder, which is why they cannot separate an inverted triangle from an hourglass: both have a waist that is clearly narrower than the ends, and the only thing distinguishing them is whether the top of the frame outmeasures the hip.
None of the four is used on its own. Every rule below is a comparison between two of your own numbers, so the unit cancels and the classification is the same in inches or centimeters. This is also why a shape is not a size: a ratio does not know how large the measurements are, only how they relate.
The rules, in order
Five tests run top to bottom, and the first one to fire is the answer. The order is the part most calculators get wrong.
1 · hip > max(bust, shoulder) × 1.05 → PEAR
2 · max(bust, shoulder) > hip × 1.05 → INVERTED TRIANGLE
3 · waist ÷ bust or waist ÷ hip ≥ 0.85 → APPLE
4 · waist ÷ bust and waist ÷ hip ≤ 0.75 → HOURGLASS
5 · nothing above fires → RECTANGLE
Tests 1 and 2 ask which end of the frame is wider. Tests 3 and 4 ask how defined the waist is. Dominance is checked first on purpose: a figure measuring 36-33-40 has hips four inches past the bust and a waist that is not especially drawn. Run the waist test first and it returns rectangle, which is the wrong advice for a body that is visibly wider at the hip. Run dominance first and it returns pear, which is right.
Rectangle is last because it is the residual, not a positive finding. It is what you get when neither end dominates and the waist is neither notably defined nor notably full — the middle of the distribution, and the most common single answer.
Where the numbers come from
There is no published standard for these thresholds. No sizing body, medical authority or academic group defines where a pear becomes a rectangle, and anyone who implies otherwise is inventing an authority that does not exist. Body shape is a styling convention, not a taxonomy.
The three numbers used here — 1.05 for dominance, 0.85 for a full waist and 0.75 for a defined one — were fitted to the ratios that the widely used calculators already agree on, so a figure classified here gets the same answer it would get elsewhere. The 5% dominance margin exists because measurement error is real: a padded bra or a tape held half an inch off level moves a reading by more than an inch, and a threshold with no tolerance would flip shapes on noise.
If enough real measurements suggest the cut-offs sit in the wrong place, they are the two numbers to move, and this page will say so when they change.
What the method cannot see
- The spoon. A spoon figure is a pear with a distinct shelf at the upper hip. Four circumferences cannot detect a shelf, so the calculator returns pear for a spoon and the spoon page says so plainly.
- Height and vertical proportion. The same four measurements on a 5'1" frame and a 5'10" frame produce the same shape but not the same styling answer. That is why height appears as a sub-type on each shape page rather than as an input here.
- Where the weight sits front to back. A tape measures a circumference, not a profile. Two people with identical numbers can carry them very differently.
- Your own measuring. Realistically the largest source of error in the whole system is the tape, not the rules. Measure twice.
See it run
The calculator prints the line that produced your result, so you can check it against the rules above.
Run the calculator