The vernier scale adds an extra degree of accuracy to measurements. On the vernier scale, the smallest increment on the main scale is further divided.
The metric vernier scale is divided into 50 equal parts. The measuring range of the vernier scale is usually 1mm, with each increment representing 0.02mm.
On an imperial caliper with a main scale of 6 inches, the vernier scale is 0.6 inch long, and is divided into 25 parts. Each increment has a length of 0.001 inch.