Gear ratios and speed, cadence, gear tables, chain length, wheel circumference, climb grades, saddle height and frame size.
payments ON MAINNET (real money) · 8 live endpoints
| Endpoint | Price | What it answers |
|---|---|---|
GET /cadence-for-speed | $0.02 | Cadence needed to hold a target speed in a given gear, and the chainring-to-cog ratio needed for a speed at a cadence. |
GET /chain-length | $0.02 | Chain length in links, rounded up to even, from chainstay length and chainring and cog teeth, with the exact figure. |
GET /climb-gradient | $0.02 | Gradient percent and angle from rise and distance, plus climbing rate (VAM) and the time to climb at a given rate. |
GET /frame-size | $0.02 | Rough bike frame size (seat tube cm and S/M/L) from inseam by bike type, with a height-based letter size cross-check. |
GET /gear-ratio | $0.02 | Gear ratio, gear inches, development per pedal turn and speed at a cadence for a chainring and cog on a given wheel. |
GET /gear-table | $0.02 | Gear inches and speed at a cadence for every chainring and cog in a drivetrain, with the range, steps and duplicate gears. |
GET /saddle-height | $0.02 | Starting saddle height from inseam by the LeMond (0.883) and Hamley (1.09) rules, plus the Holmes knee-angle check. |
GET /wheel-size | $0.02 | Rolling circumference and diameter for common tyre sizes, or an estimate from rim bead diameter and tyre width in mm. |
GET /catalog returns this list as JSON. Activity hub · uptime.
Bicycle arithmetic computed locally from the numbers given, using standard formulas and common fit rules of thumb, provided as is. Fit formulas (saddle height, frame size) are starting points only: a professional bike fit accounts for flexibility, injury and riding style. Wheel circumference is best measured by rolling the loaded wheel one turn. Not a safety inspection of a bicycle. Every paid response carries a disclaimer field.