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# Learn about the metric based gearing system used by the UCI

Modern standards can take time to be adopted by an industry. This article aims to explain what development meters are, how they're calculated, and when they're useful.

### What are development meters?

Development meters is the distance in metres the bicycle travels with each pedal stroke.

### How are development meters calculated?

This system is a bit more cumbersome to calculate than the gear inch system due to having to use an irrational constant. It's measured in metres and can be calculated by multiplying the circumference of the driven wheel by the gear ratio.

Development meters can be calculated from the following formula, where TT stands for tire thickness, RD for rim diameter, GR for gear ratio, and DM for development meters.

$(TT × 2 + RD) × pi × GR = DM$

### Where can measurements be found?

The thickness of the tire is measured across its tread, and the diameter of the rim is measured up to its bead. Both are measured in millimeters. A marking can also be found printed on the sidewalls of the tire. To learn more about tire sizes, please visit our articles covering the individual sizing systems.

### When should development meters be used?

Development meters are most commonly used in countries that have adopted the metric system. They're useful when the wheel sizes differ, however they're less effective when the crank arms are of different lengths. It's recommended to use development meters prior to changing the tire width or rim diameter.