Guide:How to measure your eyesight
Measuring your eyesight can be done in several different ways.
Centimetre measurements are seeing your distance to blur with a tape measure held against a screen, usually.
A Snellen chart is good as it controls a lot of variables. If you stand at the same distance with the same given pair of glasses in similar, or same lighting and notice an improvement over time, then it's safe to say your eyesight is improving.
Real world object
This usually works best with signs. Take a given object, preferably with text that you see very frequently and see whether there's an improvement over time in how well you can see the object.
This one might not produce hard figures like the other two methods, so it's better to use this exclusively only once you're sure you're getting improvements as verified by the other methods that produce numbers.