How to measure the least count of the instrument???

Least count is the minimum measurement that can be made by a measuring device.

Least count of a vernier callipers = minimum measurement on main scale / total number of divisions on vernier scale.

Let’s derive this:

Where S is the value of 1 Main scale division and N is the number of equal divisions on the vernier scale.

Least count of a screw gauge = minimum measurement on main scale / total number of divisions on

Smaller is the magnitude of least count of a measuring instrument, more precise the measuring.