Knowing the right measurement for your frames is important when shopping for glasses online. Check the inside of the temple arm and there should be some numbers there. These numbers are your frame measurements.
If you can no longer read the numbers on the inside of your frame, you can always try measuring by hand. Just remember, when measuring frame width, you need to measure from temple screw to temple screw. For temple length you need to measure from the temple screw to the temple tip.