About

Optimizing a bicycle drivetrain requires balancing torque for climbing against resistance for speed. This calculator quantifies mechanical advantage using Gear Inches and Development (meters traveled per crank revolution). Cyclists use these metrics to compare 1x setups against traditional double chainrings. A small change in tire circumference or cassette range significantly alters the cadence required to maintain a specific speed. Accurate configuration helps in selecting the correct parts for criterium racing, gravel grinding, or loaded touring.

Formulas

The distance a bicycle travels in one pedal stroke is defined as Development.

Dev = C_tire × Teeth_frontTeeth_rear

To determine speed from cadence, convert units appropriately.

Speed_kph = Dev × RPM × 601000

Reference Data

Metric	Formula Concept	Typical Road Value
Gear Inches	D_wheel × (T_front / T_rear)	30 to 120
Development	C_tire × Ratio	2.5 m to 9.5 m
Speed	Development × RPM × 0.06	25 to 45 km/h

Frequently Asked Questions

Gear Inches is a historical unit indicating the diameter of the wheel if the bicycle were a penny-farthing (direct drive). Higher numbers mean harder pedaling and higher top speed.

Use the ISO sizing (e.g., 25-622 for a standard 700c road tire). The tire width adds to the total diameter, affecting the rollout circumference.

Modern 1x systems simplify shifting but may have larger jumps between gears. Comparing them helps visualize if you lose top-end speed or low-end climbing ability.

No. Gear ratio is mechanical. However, your speed is directly proportional to cadence (RPM) for any fixed gear ratio.