Short answer: less than the number on the box, and the gap is bigger than most brands admit.
Air-cushion and foam lifts compress the moment you put your bodyweight on them. The height printed on a listing is almost always the unloaded height, measured with nothing pressing down on it. The height you care about is the one you stand at.
Why the advertised number is never the standing number
Three things eat into it:
- Your bodyweight. The heavier you are, the more the cushion compresses. Two people can wear the same lift and stand at measurably different heights.
- The shoe's own sole. A soft running-shoe midsole compresses underneath the lift as well, so you lose height twice. A firm leather-soled dress shoe or a boot loses far less.
- The material. Air chambers give the most comfort and compress the most. Dense EVA or silicone compresses less but transmits more impact.
How to measure what you actually gained
Do not measure the insole. Measure yourself.
- Stand barefoot against a wall on a hard floor. Mark the top of your head. That is your baseline.
- Put on the shoes you will actually wear, with the lift in, and stand normally against the same wall. Mark again.
- The difference is your real gain, including the height the shoe itself was already giving you.
Do it on a hard floor, not carpet, and stand naturally rather than pushing up. Most people are surprised twice: first that the lift gives less than advertised, then that their shoes were already adding more than they realised.
What to expect from each tier
Our lifts come in nominal heights of 1.2 in (3 cm), 2 in (5 cm), 2.75 in (7 cm) and 3.5 in (9 cm). Expect your standing gain to come in somewhat under those numbers, with the loss growing as the lift gets taller and softer.
We are not going to invent a precise percentage we have not measured. Any brand quoting an exact compressed figure without saying how they tested it, at what bodyweight, in what shoe, is guessing at you. We are testing each tier and will publish the measured standing heights, along with the test conditions, on this page.
What this means for choosing a height
Two practical consequences:
- Do not buy a taller lift to compensate for compression. Concealment and comfort fall off much faster than height rises. A 3.5 in lift that is visible and uncomfortable is worse than a 2 in lift you forget you are wearing.
- Firm shoes give you more of what you paid for. If you want maximum real-world gain, wear the lift in a boot with a firm sole rather than a soft trainer.
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