Gear ratio calculator for fixed gear

More announcements

For fixed and single-speed: gear ratio, skid patch wear points, metre development, gear inches, and gain ratio, cadence-speed table, and equivalent chainring pairs ±2%.

What we count

Ratio Skid patch Development, m Gear inches Gain ratio Cadence ↔ speed Equivalents ±2%

The link to the page saves your layout — you can throw it into the chat and argue about the transfer in a substantive way.

Basics

Front chainring, teeth Rear sprocket, teeth Rim, ETRTO Tire width, mm Crank length Your circumference, mm Target speed, km/h Ski jump from two feet

Calculating by ETRTO 622-23.

Analysis

Wear points from the leading leg Addition from the discount with both feet

Ratio (gear ratio)

2.56

Skid patch

Development

5.36 m

Gear inches

67.2″

Gain ratio

5.02

Speed at 90 rpm

28.9 km/h

All-round: city, casual rides, calm flats.

Off the bat: 9 points.

Per pedal revolution.

Cadence / speed

Cadence for target speed

90 rpm

90 rpm is highlighted as a landmark. If more than 110 is obtained for the desired speed, the transmission is too short, less than 70 is too long.

Equivalent gears ±2%

Pairs of chainrings with almost the same gear ratio. Click on any to substitute it into the calculation.

How to read it

Ratio — how many revolutions the wheel makes per revolution of the pedals. Below 1.9 — bike polo and stunts, 2.3-2.7 – universal urban range, above 3.2 — track and sprint.

Skid patch — the number of points on the tire that wear out during a skid. Calculated as the rear teeth divided by the GCD with the front teeth: the more points, the smoother the wear. If after reduction the front chainring is odd, a two-legged skid doubles the number of points.

Development — the meters that the bike passes in one turn of the pedals. Gear inches is the same in inches of the equivalent penny-farthing wheel, the usual currency in conversations about fix.

Gain ratio — Sheldon Brown measure: the ratio of the distance traveled to the distance traveled by the pedal. Takes into account the length of the connecting rod, so it's more honest to compare gears on different curves.

We take the circumference of the wheel according to ETRTO as π × (rim diameter + two tire widths). For accuracy, you can enter your own rollback measurement — the same way a bicycle computer is calibrated.

The idea and method of calculating the skid patch is from the Fantastic Fixed Gear Calculator of the SURFACE team and Sheldon Brown's tables.

Link to this layout