An internal hub gear (IGH) has its gearing mechanism sealed inside the rear hub. Popular brands include Shimano Nexus/Alfine, Sturmey-Archer and Rohloff. They are low-maintenance and shift while stationary.

How do hub gears work?

Internal gears multiply or divide the input rotation using planetary gear sets. Each gear position has a fixed multiplication factor applied to the external gear ratio.

What hub type should I choose?

3-speed is good for flat commutes. 7-8 speed covers most urban riding. For touring or hilly areas, the Rohloff 14-speed or Shimano Alfine 11 offer wider range.

BikeCalcs

Hub Gear Calculator — Internal Hub Ratios

Calculate effective gear ratios for internal hub gear systems.

Hub TypeInternal hub model — sets the fixed planetary gear ratios (3-spd Sturmey-Archer AW 177%, 5-spd Nexus 206%, 7-spd Nexus 245%, 8-spd Nexus/Alfine 307%)

Chainring Teeth

Number of teeth on the front chainring

Sprocket Teeth

Teeth on the rear cog driving the hub (typically 16–22 on hub-geared bikes)

Wheel Circumference

Rolling circumference in mm (e.g. 700×25C ≈ 2105 mm, 26-inch ≈ 2070 mm) — not the wheel diameter

How We Calculate This

Hub Gear Calculation

Effective Ratio = External Ratio × Internal Multiplier

Each hub type has fixed planetary ratios set by the manufacturer (e.g. Sturmey-Archer AW 0.75 / 1.0 / 1.333, Shimano Nexus 8-speed 0.527 → 1.615). The effective gear ratio is the external ratio (chainring ÷ sprocket) multiplied by each internal ratio. Speed at the reference cadence is then (effective ratio × wheel circumference in mm × cadence × 60) ÷ 1,000,000 km/h, following the Sheldon Brown gear-development method.

Frequently Asked Questions

Related Calculators

Gear Ratio Calculator

Calculate gear ratios from chainring and sprocket tooth counts.

Gear Inches Calculator

Convert gear ratios to gear inches for comparison.

Development Calculator

Calculate distance travelled per pedal revolution for any gear.

Chainring Calculator

Compare chainring sizes and their effect on gearing range.

Cassette Calculator

Analyse cassette tooth counts and gear jumps between sprockets.

Last updated: 2025-02-20

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.