What is LC in Vernier scale

LC (Least Count) in a vernier scale is the smallest measurement the instrument can accurately resolve, calculated using the formula: LC = 1 MSD - 1 VSD, where MSD is one main scale division and VSD is one vernier scale division. Alternatively, it's expressed as LC = (Value of smallest main scale division) ÷ (Number of vernier divisions). For a standard vernier caliper with 1 mm main scale divisions and 10 vernier divisions spanning 9 mm, the least count is (1 mm ÷ 10) = 0.1 mm.

The least count represents the fundamental precision limit of the vernier caliper and determines the instrument's suitability for specific applications. A 0.1 mm LC caliper works adequately for general workshop measurements where tolerances are ±0.2 mm or greater, while a 0.02 mm LC vernier is necessary for precision machining with tighter tolerances. The vernier principle achieves this enhanced precision by creating a secondary scale with divisions slightly smaller than the main scale divisions—when the zero of the vernier aligns between main scale marks, exactly one vernier line will coincide with a main scale line, and that vernier line number indicates the fractional measurement. Understanding least count is critical for quality control work, as attempting to measure dimensions with tolerances smaller than the instrument's LC produces unreliable results subject to reading errors and insufficient resolution. Always select measuring tools with least count at least three to five times finer than the tolerance you're trying to verify.