A forum member asked me about calculating the lens magnification for macro shots. There are many references on the web that give formulas ranging from simple division to complex calculus. But I think a way that makes more sense to me is a simple visual method.
If your camera has a APS-C sensor its' size is 22.7mm X 15mm. Take a shot of a ruler marked in mm and count the number of divisions that show up. If 23 lines show up then you are shooting at 1:1. If say 46 lines show up you are shooting 1:2. If only 11 or 12 show up you are shooting at 2:1.
One thing to note, a 1:1 macro lens will give life size magnification at minimum focusing distance. Move further away from the subject and you will lose this 1:1 ratio.