Hourglass body shape

What the rule says

Three conditions. Bust minus hips is 1 inch or less, so the bust may lead the hips by at most an inch. Hips minus bust is under 3.6 inches, so the hips may lead the bust by anything less than that. And the waist is defined: at least 9 inches (22.9 cm) smaller than the bust, or at least 10 inches (25.4 cm) smaller than the hips. The first two conditions are not symmetrical — the rule tolerates more hip lead than bust lead — and the third is the demanding one.

In our ANSUR II analysis (1,986 Army women, applying ANSUR’s chest and navel-level waist fields to the rules), 0.6% of records met the full hourglass rule. That sample is not representative and the measurement protocols differ from this site’s, so the figure describes that experiment only.

The hourglass family

Top and bottom hourglass

Both keep the defined waist and relax one end. Top hourglass allows the bust to exceed the hips by more than 1 inch and less than 10, provided bust minus waist is 9 or more. Bottom hourglass allows the hips to exceed the bust by at least 3.6 and less than 10 inches, provided hips minus waist is 9 or more — and it requires the high-hip measurement, because the same three numbers with high hip ÷ waist of 1.193 or more match Spoon instead. That is one reason the calculator sometimes asks for a fourth number.

How nearby results differ

Results are decided by the full rule set in order, so a single number crossing a threshold does not by itself guarantee a particular other result. With that said: if the waist condition fails, the Rectangle conditions hold (bust and hips less than 3.6 inches apart, waist no larger than either and within the limits) and no earlier rule matches, the result is Rectangle. If the bust moves more than an inch and less than 10 ahead of the hips with the 9-inch bust-to-waist drop intact, Top hourglass. If the hips move 3.6 or more ahead of the bust, the result depends on the waist and high hip: Bottom hourglass, Spoon or Triangle. Spoon is checked after Hourglass but before Triangle and Rectangle, so a body that misses the hourglass waist condition, has hips more than 2 inches over the bust and a waist 7 or more under the hips, and has high hip ÷ waist of 1.193 or more returns Spoon rather than Rectangle — bust 37.5, waist 30.1, hips 40, high hip 37 inches, for example. The calculator reports which measurement, changed by how much, would alter your result.

The word and the rule

“Hourglass” is also used informally, without a fixed measurement threshold, for any body with a visibly smaller waist. Under the rule it means the relationship above. If you have been described as hourglass and the calculator returns Rectangle, one possible reason is that your waist is smaller than your bust and hips, but by less than the 9- or 10-inch drop the rule requires; the result shows how far short it is.

What the label does not mean

It does not describe height, weight, bone structure or front-to-back depth; it describes three circumferences. It is not a ranking: FFIT was built for apparel sizing, and hourglass is one category among nine, not the target the others fall short of. The outfits page for this family lists options for emphasising the waist or exploring other silhouettes; none of them is required.

• Outfit options: hourglass outfits
• Comparing hourglass and pear results: hourglass vs pear
• Where each measurement is taken: how to measure
• The full rule set and its sources: methodology

References

The rules and figures on this page come from the sources below. Reference values are conventions from the literature, not targets.

1. Simmons, Istook & Devarajan (2004). Female Figure Identification Technique (FFIT) for Apparel, Part I: Describing Female ShapesJournal of Textile and Apparel, Technology and Management 4(1):1–16 · JTATM 4(1)Defines the nine FFIT shapes (hourglass, top and bottom hourglass, spoon, triangle, inverted triangle, rectangle, diamond, oval) from bust, waist, high-hip and hip circumferences on 3D body scans of North American women. The rules on this site are this set, as later revised.
2. Sokolowski (2020). Modification of the Female Figure Identification Technique (FFIT) Formulas to Include Plus Size Bodies3DBODY.TECH 2020 Conference Proceedings · proc.3dbody.tech/2020Shows the 2007 FFIT formulas assumed the waist is smaller than the bust and so failed on many larger bodies; adds the Diamond and Oval rules and a ≥ 0 lower bound to Triangle, Inverted Triangle and Rectangle. This site uses the revised formulas.