Two different questions, one tape measure
A body type calculator answers two things that get tangled together constantly. The first is proportion — how your shoulder, waist and hip measurements relate to each other, which decides what clothes hang well and what a training programme should emphasise. The second is risk — where you carry fat, which is one of the better cheap predictors of cardiometabolic disease we have. The first is aesthetics. The second is medicine. Keeping them separate is most of the value on this page.
Shape comes out as a label: rectangle, triangle, inverted triangle, hourglass, oval. Risk comes out as two ratios, and those are the numbers worth writing down.
The ratios that predict something
Waist-to-hip ratio (WHR)
WHR is a proxy for where fat sits. Fat above the waist — visceral fat, packed around the organs — is metabolically active and drives insulin resistance, dyslipidaemia and blood pressure. Fat below the waist, in the hips and thighs, is comparatively inert. So a high waist relative to hip means the fat you have is in the expensive place. The WHO thresholds:
| Risk band | Men | Women |
|---|---|---|
| Low | < 0.90 | < 0.80 |
| Moderate | 0.90 – 0.99 | 0.80 – 0.84 |
| High — substantially increased risk | ≥ 1.00 | ≥ 0.85 |
The catch with WHR is that it can be gamed by the denominator: gaining muscle in the glutes improves the ratio without changing anything about your visceral fat. Which is why the second ratio has largely overtaken it.
Waist-to-height ratio (WHtR) — the 0.5 rule
One threshold, no lookup table, no sex or age adjustment, and it consistently outperforms BMI for predicting cardiometabolic outcomes. The UK's NICE guidance now recommends it alongside BMI for exactly that reason. Under 0.5 is the target; 0.5 to 0.6 is increased risk; over 0.6 is high. If you only remember one number from this page, remember that your waist should be under half your height.
WHtR is also the honest progress marker during a fat-loss phase, because the denominator cannot move. See the body fat calculator for the percentage version of the same tape measurements, and the ideal weight calculator for the weight range those numbers usually correspond to.
How the shape rules work
The published shape rules are stated as whole-inch differences between the three measurements, so that is how this calculator evaluates them (metric inputs are converted first). They are applied in order, and the first match wins:
| Shape | Rule |
|---|---|
| Oval | Waist ≥ hip |
| Hourglass | Shoulder and hip within 1″, and waist 9″+ narrower than the shoulder or 10″+ narrower than the hip |
| Inverted triangle | Shoulder ≥ 3.6″ wider than hip |
| Triangle (pear) | Hip ≥ 3.6″ wider than shoulder |
| Top / bottom hourglass | One end 1–3.6″ wider, with a 9″+ waist gap on that side |
| Rectangle | Everything else — no dominant point |
Because these are hard cut-offs on soft measurements, a centimetre of tape tension can move you between two shapes. Treat the label as a description of your current proportions, not an identity.
Somatotypes: where they came from, why they mostly aren't used
Ectomorph, mesomorph and endomorph come from William Sheldon's 1940s constitutional psychology, which classified thousands of photographed students into three builds and then claimed each build carried a matching temperament — endomorphs sociable, mesomorphs assertive, ectomorphs withdrawn. The personality half of the theory collapsed under scrutiny and was abandoned. The physique half survived in fitness culture, where it got quietly reinterpreted as three metabolic types with three prescribed diets.
That reinterpretation is not supported. There is no evidence that people sort into three discrete metabolic categories, and no evidence that matching a diet to a somatotype outperforms matching it to body weight and activity. What is real: skeletal frame varies, and people differ in how readily they gain fat or muscle. Both are continuous, both are partly heritable, and neither is captured by a three-way label.
So this calculator reports a tendency, built from two things a tape can actually measure — frame width (height ÷ wrist circumference) and central fatness (waist ÷ height). If your numbers do not lean one way, it says “mixed”, which is the correct answer for most people.
What this means for training
Proportion is genuinely useful programming information, once you drop the somatotype framing:
- Inverted triangle — you already have the taper. Additional pressing makes the imbalance worse, not better. The under-trained half is almost always legs and posterior chain.
- Triangle — lateral delts and upper back are the highest-leverage additions, because widening the shoulder shifts the ratio without needing to shrink the hip.
- Rectangle — the most responsive shape, because there is nothing to work around. Shoulder width plus waist reduction changes the silhouette faster here than anywhere else.
- Hourglass — proportions are already balanced; training is about total muscle and body-fat level, not redistribution.
- Oval — this is the one where the priority is the waist itself, not the silhouette. Start with a calorie target from your TDEE and let the shape follow.
The uncomfortable summary: shape sets which muscles are worth emphasising, and body-fat level sets whether anyone can see the result. Almost every request to “change my body type” is answered by the second one.