Methodology
What the labels mean, how metrics are defined, and what we do not claim.
Value classes
- Manufacturer stated
- Published by the brand (product page, press kit, spec sheet). Recorded verbatim with the source URL and access date. Brands differ in whether stack height includes the insole; we record the brand’s figure and note the convention when known.
- Externally measured
- Measured by a third party with a stated method (for example a review lab with calipers or a flex rig). The source and method are recorded; sizes vary between labs.
- AI estimated
- Estimated by our image-analysis pipeline from a public side-profile photograph. Always carries an algorithm version, a confidence score and the input image’s provenance. Values are relative (percent of shoe length), never absolute millimetres.
- Derived
- Computed from other recorded values (for example a composite rocker index). The formula is versioned.
When several values exist for the same metric, the page shows one by precedence: measured › manufacturer stated › derived › AI estimated, then higher confidence, then the most recent. All approved observations remain visible on the shoe page; nothing is deleted when a better method appears.
Confidence
Each observation has a confidence between 0 and 1, set by the extractor or algorithm that produced it and shown as High, Medium or Low. Confidence describes how certain we are that the number faithfully represents the source, not how accurate the source itself is. Values below the auto-approval threshold are held for human review before they appear.
Rocker onset and related geometry
With the shoe resting on a flat surface, viewed from the lateral side, we fit a ground line to the sole’s contact zone and measure how far the outsole lifts off that line at each point along the length. Rocker onset is the position, from heel (0 %) to toe (100 %), where the forefoot begins to lift and stays lifted. Toe spring (relative) is the height of the toe tip above the ground line as a percentage of shoe length. Heel bevel onset is the same idea at the rear. These are relative quantities so they can be read from an uncalibrated photo; they are compared across shoes, not against lab millimetres.
Metric definitions
| Metric | Unit | Definition |
|---|---|---|
| Heel-to-toe drop drop_mm | mm | Difference between heel and forefoot stack height. |
| Heel stack heel_stack_mm | mm | Total sole thickness under the heel (midsole + outsole, sometimes insole, per source convention). |
| Forefoot stack forefoot_stack_mm | mm | Total sole thickness under the forefoot. |
| Weight weight_g | g | Weight of one shoe. Size varies by source; see size_variant on the observation. |
| Rocker onset rocker_onset_pct | % | Position along the shoe length (heel = 0 %, toe = 100 %) where the forefoot sole begins to lift from the ground plane. Lower = earlier rocker. |
| Rocker curvature rocker_curvature_score | score | Relative strength of forefoot curvature, 0 (flat) to 100 (very aggressive). Method-specific. |
| Toe spring toe_spring_mm | mm | Height of the toe tip above the ground plane, in millimetres (only from calibrated sources). |
| Toe spring (relative) toe_spring_relative | % | Toe-tip height above the ground plane as a percentage of shoe length (image-derived, uncalibrated). |
| Heel bevel onset heel_bevel_pct | % | Length of the bevelled heel region as a percentage of shoe length, measured from the rear. |
| Heel bevel angle heel_bevel_angle_deg | deg | Angle of the heel bevel relative to the ground plane. |
| Longitudinal stiffness longitudinal_stiffness_score | score | Resistance to bending along the shoe length, 0–100 relative scale. Method-specific. |
| Forefoot flex stiffness forefoot_stiffness_score | score | Resistance to bending at the metatarsophalangeal flex zone, 0–100 relative scale. |
| Torsional stiffness torsional_stiffness_score | score | Resistance to twisting about the long axis, 0–100 relative scale. |
| Rocker Index rocker_index | score | Composite 0–100 score combining rocker onset, curvature and toe spring. Derived; definition versioned via algorithm_version. |
What we do not claim
ShoeGeometry describes products. It does not assess individuals, diagnose conditions or recommend treatment. Image-derived values are estimates and are labelled as such. Sources are credited and linked; we store brief factual extracts and our own derived numbers, not copies of copyrighted articles or photographs.