Understanding Gears
Change a gear. See how far you travel and how fast you pedal.
Change gears
What this gear means
- Gear ratio
- wheel turns per pedal turn
- Distance per pedal turn
- Required cadence
- Speed
- Estimated power needed
Based on selected ride conditions; your actual power may differ.
More details
- Gear range
- Gear inches
- Wheel turns per minute
The power model estimates steady riding and does not include acceleration; at fixed speed, shifting changes cadence but not estimated power.
Cadence guidance uses general teaching ranges, not individual fitness limits; a moderate cadence does not establish that the speed is sustainable.
Ride conditions
Flat 0% · Gentle 3% · Moderate 6% · Steep 10%
These settings affect estimated power; they do not change the gear ratio.
View all gears
Gear numbers run from the lowest ratio to the highest. Similar ratios are marked as near overlaps; the nominal combination count does not mean every ratio is distinct. Select a row with Enter or Space.
Setup details
How to read this setup
2×10 means two front chainrings and ten rear sprockets. T abbreviates teeth. Rear endpoints do not identify all intermediate gears. Phase 1 supports one or two front chainrings.
Tire sizes show a familiar name where available, followed by International Organization for Standardization (ISO) width and rim bead-seat diameter in millimeters.
Advanced Settings
Illustrative model settings. All bike presets use the same surface and riding position until you change them.
Estimated from elevation using standard dry-air conditions. Actual air density varies with temperature, air pressure, and humidity. Use Custom density if you have a better estimate.
Expert values
Drag area is drag coefficient multiplied by reference area (CdA). The rolling resistance coefficient (Crr) and efficiency have no units.
Use Edit to enter measured wheel circumference. The estimate uses nominal tire size; load and pressure can affect the actual value.
Optional comparison with your chosen planning target, not a fitness assessment.
Compare Setups
Compare your current gearing with another setup at the same ride conditions.
Current Setup
Comparison Setup
Selected Gears Compared
| Result | Current Setup | Comparison Setup |
|---|
Based on selected ride conditions; your actual power may differ. Change ride inputs and physics in Understanding Gears.
Full Setups Compared
| Metric | Current Setup | Comparison Setup |
|---|
Compare effective gear ranges
Both bars use the same distance-per-pedal-turn scale. Further left means lower effective gearing.
View all gears compared
Gear numbers identify combinations within each setup, not equivalent gears across setups; read the ratio and distance to compare them. Scroll sideways on narrow screens.
| Current Setup | Comparison Setup | ||||
|---|---|---|---|---|---|
| Gear · front × rear | Ratio | Distance / turn | Gear · front × rear | Ratio | Distance / turn |
Plan a Climb
Choose a slope, power target, and pedaling rate. See which setups offer a low enough gear.
180 W is an example, not an estimate of your capability.
Pedal revolutions per minute; a planning preference.
Estimated climbing speed
Distance needed per pedal turn
Equivalent ratio for Current Setup’s wheel: . Matching below uses each setup’s own wheel size.
| Setup | Lowest ratio | Lowest distance / turn | Cadence in lowest gear | Result |
|---|
“Meets target” means the lowest gear allows at least your target cadence at the estimated speed. “Lower cadence needed” does not mean the climb is impossible. These calculations do not assess component compatibility or fitness.
About this v0.7 review
October 3, 2026. Updated against consolidated specification v0.7, including mode-aware guidance, explicit speed defaults, closest-gear matching, setup identification, and the climbing workflow.
Review copy: calculations and interactions run locally. The drivetrain animation is a simplified teaching schematic. No accounts, external resources, analytics, network calls, or local storage are used. Sharing puts settings into the link only.
Calculation and application-state checks were run in a simulated document environment. Live browser, visual layout, keyboard, and screen-reader checks remain outstanding because browser access was unavailable during this build.
This HTML prototype uses plain JavaScript. The specification’s production TypeScript architecture and deployment security gate remain release work; this file is not a certification of production readiness.