The least count of an instrument is the smallest measurement that can be taken accurately with it. Pierre Vernier of France invented Vernier callipers, an instrument for making highly specific linear measurements, in 1631. For quality control measurements, Vernier Calipers are commonly used in scientific laboratories and manufacturing.
Least count of Vernier Calliper
Least count of Vernier calliper= Smallest division on main scale/Number of divisions on Vernier scale.
Least count of Vernier calliper = 1mm/10 divisions
Least count of Vernier calliper = 0.1 mm