How it works
The workflow, examples and limits behind every tool.
Gear speed ↗
km/h = circumference in mm × front/rear × cadence × 60 ÷ 1,000,000.
Example: 2100 mm circumference, 50/25 gearing and 90 rpm give 22.68 km/h.
Ideal drivetrain only; no wind, gradient, power or real-world speed prediction.
Cadence target ↗
Cadence = speed × 1,000,000 ÷ (60 × circumference × front/rear).
Example: 22.68 km/h with 2100 mm rollout and 50/25 gearing needs 90 rpm.
A kinematic conversion, not training or medical advice.
Gear range ↗
Range percent = (large chainring/small sprocket) ÷ (small chainring/large sprocket) × 100.
Example: 50/34 chainrings and 11–34 sprockets give about 454.545% range.
Does not certify derailleur capacity, chain length or component compatibility.
Wheel rollout ↗
Circumference = π × measured outside diameter.
Example: A 700 mm measured outer diameter gives about 2199.115 mm circumference.
700 mm is an example outer diameter, not a claim about the 700C rim standard. A loaded rollout measurement is more useful.
Local work, explicit limits
Each workspace reports its input and file limits. Imports validate the supported format before asking to replace saved work. Plain text is displayed as text, never executed as markup. Both languages use the same tools; the root address always opens in English, with Chinese under /zh/.