How the numbers
are made.

Economy gain, expressed as a range

Laboratory studies of advanced footwear technology — Hoogkamer, Barnes & Kilding, Hébert-Losier and others — consistently report improvements in running economy of roughly 2.5% to 4.5% against a traditional racing flat. What gets quoted as “4%” is the headline mean from the original Nike Vaporfly work, not a figure any individual runner is guaranteed.

The spread between individuals in the same shoe is large — some runners get almost nothing, a few get more than 6%. Reporting a single number would be dishonest, so every shoe here carries a band, and every estimate on the site is presented as a range.

Bands are assigned by tier — current flagship racers sit highest, second-tier super shoes below them, nylon-plated and value racers lower again — informed by published comparative testing where it exists for that model. They are a considered judgement, not a lab measurement of each specific shoe.

Economy is not time

Using less oxygen at a given speed does not translate one-for-one into a faster finish. Drag rises with the square of velocity, and the metabolic cost of running is not linear either. Hoogkamer's work found that a 4.0% improvement in running economy produced roughly a 2.6% improvement in velocity at elite marathon pace.

We use that ratio — 0.65 — to convert economy gain into speed gain. So a shoe giving a 4% economy improvement is modelled as making you 2.6% faster, not 4% faster. A great many “super shoe calculators” skip this step and overstate the benefit by more than half.

The benefit shrinks if you are slower

This is the part the marketing never mentions. The plate-and-foam system needs force to compress and rebound. Nearly all the published testing was done on runners moving at 14–18 km/h — roughly 3:20 to 4:20 per kilometre. Below that, measured benefits get smaller and much more variable, and for some runners they disappear.

So the calculator applies a pace adjustment: full effect at 16 km/h and above, tapering to about 70% at 10 km/h (6:00/km) and 45% at 7 km/h (8:34/km), interpolated in between.

This is the biggest assumption on the site. It is an informed model rather than a measured curve, because no one has published a clean dose-response curve of benefit against pace across the recreational range. It is deliberately conservative. If you are running a five-hour marathon, the honest answer is that nobody knows precisely what a super shoe does for you, and it is probably less than the box implies.

What you are comparing against

A gain has to be a gain over something. The literature's baseline is a traditional non-plated racing flat, which is not what most people are actually racing in. So the calculator lets you set your current shoe and subtracts what you have already banked:

This is why upgrading from an old carbon shoe to a new one shows a much smaller saving than the brand's launch material suggests. That is correct, and it is usually the most useful thing the calculator tells you.

Cost per race and cost per second

Super shoe foams degrade fast. Most of these shoes stop delivering their benefit somewhere between 120km and 300km — long before they physically fall apart. The per-shoe figure in the index is competitive life, not structural life.

A race consumes more than its own distance: warm-up, strides, and at least one tune-up session in the shoe beforehand. We assume each race cycle uses 1.5× the race distance. Cost per race is then RRP divided by the number of race cycles the shoe supports.

Cost per second saved is RRP divided by the total time saved across the shoe's whole life. It is the single most clarifying number here. A £450 shoe with a 120km life used for marathons works out very differently from a £230 shoe with a 260km life, even when the faster shoe genuinely is faster.

What this cannot tell you

Fit, and whether the shoe suits your gait, matter more than any of this. A shoe with a 4% economy gain that gives you a black toenail at 30km is slower than one with 3% that does not. The index flags fit width and stability for that reason, but nothing substitutes for trying them on.

These estimates also assume you are healthy and the shoe is new. There is an ongoing and unresolved discussion about injury risk from training heavily in high-stack plated shoes — that is a question for a physiotherapist, not a calculator.

Nor does the model account for course, weather, or how the shoe feels at 35km when your form has fallen apart. It gives you a defensible number to put next to a price tag. That is all, and it is more than the market currently offers.

Data and corrections

Specifications are manufacturer-stated for a men's US 9 / UK 8 unless noted. Where a figure is inferred from a previous generation rather than a published spec, the shoe is marked specs est. so you know to check it. Regulations are summarised from World Athletics Book C, C2.1A. Index last reviewed 2026-08-13.

If something here is wrong, it should be fixed rather than defended — get in touch.