The smallest value that can be measured by the measuring instrument is called its least count.

– All the readings or measured values are good only up to this value.

– Error associated with resolution of the instrument is called least count error.

– Least count of vernier is $0.01 \mathrm{~cm}$ and least count of spherometer is $0.001 \mathrm{~cm}$.

– Least count error belong to category of random error but within a limited size.

– It occur with both systematic and random error.

– Least count of meter scale is $1 \mathrm{~mm}$.

– Using instrument of higher precision, improving experimental technique we can reduce least count error.

Repeating the observation several times and taking arithmetic mean of all observation the mean value would be very close to the true value of the measured quantity.