Running shoe specs explained: stack, drop, weight, plates and rockers

Last updated 9 October 2026

A running shoe spec sheet is a handful of numbers and labels. Each one describes how the shoe is built, not how it will feel to you, but together they are the best way to compare a new shoe with one you already know. The figures below come from the 232 current shoes in the NextPair catalogue, each linked to the page that published it.

Stack height

Stack height is how much material sits between your foot and the ground, usually measured at the heel and at the forefoot. A higher stack generally means more foam underfoot. Of the 178 shoes with a published heel stack, the middle value is 39 mm, and 80 have a heel stack of 40 mm or more.

Drop

Drop (or offset) is the heel stack minus the forefoot stack. An 8 mm drop means the heel sits 8 mm higher than the forefoot. Two shoes can share a drop but have very different stacks: a 30/22 mm shoe and a 40/32 mm shoe are both 8 mm drop.

Across the 199 shoes that publish a drop, the most common is 8 mm (67 shoes). 10 are zero drop, meaning heel and forefoot sit at the same height.

Typical numbers by type of shoe

Middle values (medians) for current shoes that publish each figure:

Weight

Brands publish weight for one shoe at a reference size, and they don't all use the same size. A shoe weighed at men's UK 9 isn't directly comparable with one weighed at UK 10.5, so NextPair always shows the reference size next to the weight. Compare weights within the same reference size, or treat small differences as noise.

Cushioning feel

There's no standard unit for softness. Where a brand describes the cushioning (for example “firm”, “balanced” or “plush”), we record it on a five-step scale from firm to plush and link the description. Where the brand doesn't say, we leave it blank rather than infer it from the stack.

Plates

Some shoes have a stiff plate in the midsole, usually carbon fibre in racing shoes and nylon or other materials in training shoes. A plate makes the shoe stiffer from heel to toe. 21 current shoes in the catalogue have a carbon plate.

Rocker

A rocker is a curve in the sole, usually at the toe, that helps the shoe roll forward. We record it as none, gentle, noticeable or pronounced, following the brand's description.

Stability, toe box and widths

Stability shoes add features meant to guide how the foot moves, such as firmer foam on the inside or raised sidewalls. Brands label shoes as neutral, mild support or stability. Toe box describes how roomy the front of the shoe is, and many models come in wide or extra-wide versions. Width matters as much as length for fit, so check which widths a shoe comes in before you buy.

Why two sources can disagree

A brand and a retailer may measure the same shoe differently: at different sizes, with or without the insole, or at slightly different points on the heel. That's why every value on NextPair links to its source, and why we prefer the brand's own page.

Using specs to choose a shoe

Specs work best as a comparison. Start with a shoe you know you like, then look for shoes with a similar stack, drop and feel. That's exactly what finding a shoe like yours on NextPair does.