# How do you calculate aspect ratio?

The exact formula to calculate aspect ratio is inner diameter divided by wire diameter, or in shorthand:

**AR = ID ÷ WD**

Before using the formula, make sure to convert the wire gauge to millimeters or inches (to match the unit system used for the ring's ID). Our Jump Ring Sizes page contains a chart with inch and millimeter measurements for the wire gauges we sell. **Note:** Different metals use different gauge systems.

For accurate results, use calipers to measure the ID of your rings rather than relying on the mandrel size. **Two rings from different suppliers wound around the same mandrel usually yield different IDs**, because each supplier uses different tension. Rings of different gauges wound around the same mandrel also yield different IDs, because springback for the gauges is different. (For more about springback, see Common Terms.) Aspect Ratios for chainmaille jump rings generally range between 2.9 and 7.0.