How To read a vernier caliper????? Main scale reading: Note where the '0' mark of the vernier scale aligns on the main scale. In this image, it's at 27 mm. Vernier scale reading: Look along the vernier scale and find which line aligns exactly with a line on the main scale. Here, the 7.5th division (or 0.75 mm) aligns. Total reading = Main scale Vernier scale = 27 0.75 = 27.75 mm. This gives you a precise measurement combining both scales. | Aar Mech