Identify body shape from measurements.
Body shape is a description of proportion, not of size, so it comes entirely from the ratios between four measurements. Comparing hip to bust says whether the frame is balanced, top-heavy or bottom-heavy; comparing waist to both says whether there is a defined waist. Those two questions separate the commonly used categories: an hourglass has a balanced hip-to-bust ratio with a waist under about 80% of both, while a rectangle has the same balance without the waist definition.
Proportion ratios
Waist:hip = waist / hip; hip:bust = hip / bust; shoulder:hip = shoulder / hip
Classification
Balanced frame = hip:bust between 0.95 and 1.05; defined waist = waist below 80% of bust and hip
These are educational and reference calculations only. They are not a diagnosis, not a substitute for measurement or laboratory testing, and must not be used to start, stop, time or change any medication or treatment. Reference thresholds differ between national guidelines and do not account for your individual clinical context. Discuss any result that concerns you with a qualified healthcare professional, and seek urgent medical attention for acute symptoms rather than relying on a calculator.
It compares four circumference measurements as ratios. Hip divided by bust shows whether the frame is balanced; waist divided by bust and by hip shows whether the waist is defined. The category follows from those thresholds rather than from any single measurement.
Proportion drives fit. Knowing which measurement is the widest tells you where garments will need tailoring, and it is independent of weight — two people of very different sizes can share a shape.
Bust at the fullest point with the tape level, waist at the natural narrowest point between the ribs and hip bone, hip at the widest point of the seat, and shoulders straight across the back from tip to tip. Keep the tape snug but not tight and stand relaxed.