This document discusses how to calculate the least count, or smallest measurement, of metric and imperial vernier calipers. The least count is determined by the number of divisions on the main scale and vernier scale. For a metric caliper with a main scale divided into tenths of a centimeter and a vernier scale with ten divisions, the least count is 0.01 cm. For imperial calipers, the least count depends on whether the vernier scale has 25 or 40 divisions, yielding measurements of 0.001 or 0.0025 inches respectively. Calculating the least count is important for ensuring accurate measurements.

1. CALCULATION OF LEAST COUNT IN
METRIC & IMPERIAL SCALES
By: VerniersCaliper.com

2. WHAT IS A LEAST COUNT?
A scale is the defining feature of any measuring
instrument. Usually measurements are taken by
placing an object on top of a scale and noting the
distance between the edges. In this case a larger
number of divisions on the scale leads to a more
accurate measurement and vice versa.

3. The technical term used to describe this parameter is
known as least count, which is the smallest measurement
which can be measured by a scale. Its value can be
obtained by the division of one unit on the scale by the
number of divisions that lie in between.

4. REMEMBER
The correct determination of the least count of a
vernier caliper is important for the measurement to
be accurate. This is a common difficulty faced by
people, even engineers and leads to incorrect
readings while measuring heights, diameter,
lengths etc. Sometimes both metric and imperial
units together on the scale may also cause
confusion.

5. ABOUT
This article will tell you the procedure for calculating
the least count of a vernier caliper. The smallest
measurement which can be recorded by the Vernier
caliper is defined as the least count.

6. DETERMINE THE
LEAST COUNT
First we need to determine the least count of the main scale
which can be done as described previously. Then we
need to count the number of divisions on the vernier scale
and divide the least count of the main scale by it. This will
give us the least count of the vernier caliper. The formula
for this can be expressed as:
Least Count of Vernier Caliper = Main Scale least
count/ number of Vernier scale divisions

7. CALCULATION OF LEAST
COUNT OF VERNIER
CALIPERS IN METRIC SCALE
In metric scales, the units used for calibration are
millimeters i.e. one division equals 1 cm and is divided
into further divisions in millimeters. The least count can
be calculated by dividing 1 cm by the number of divisions
that lie between a unit. This way a main scale which
contains 10 divisions in a centimeter will have a least
count of 1/10 = 0.1cm or 1 mm.

8. Similarly the vernier scale is also normally divided into ten
equal parts. Count the divisions on the vernier scale just
to make sure. The least count of the vernier caliper can
now be found by dividing the least count of the main
scale by the number of divisions on the vernier scale.
Usually the least count of the main scale is 0.1 m and the
vernier scale has 10 divisions so the least count would
be 0.1/10 = 0.01cm.
The least count is related to accuracy in such a way that if
a vernier caliper has a least count of 0.01cm then it is
said to also have an accuracy of 0.01 cm.

9. if you want to calculate the least count in mm, here is the
formula below:
Vernier caliper least count in mm = Vernier caliper least
count in cm x 10
So in this case it would be; 0.001 x 10 = 0.01 mm, therefore
0.01 mm is the least count in millimeters for this Vernier
caliper.

10. CALCULATION OF
LEAST COUNT OF
VERNIER CALIPERS IN
IMPERIAL SCALE
There are two types of imperial Vernier calipers discussed
in the examples:

11. TYPE 1 IMPERIAL VERNIER CALIPERS
In a Vernier Caliper with imperial scale, the main
scale has a minimum division of 0.1 inches.
There are 40 divisions on the Vernier scale
normally in imperial Vernier Calipers. Therefore
0.1 inch of the main scale is divided into 40
divisions of the Vernier scale
So 0.1 divided by 40 = 0.0025 inch
We can say that 0.0025 inch is the accuracy and
least count for this type 1 of imperial Vernier
Caliper.

12. TYPE 2 IMPERIAL VERNIER CALIPERS
If there are 25 divisions on the Vernier Scale
If the vernier scale is divided into 25 parts then the
smallest measurement possible from the main scale
would be 0.025 inches.
Therefore least count of the Vernier Caliper is
calculated by the same formula i.e. dividing 0.025 by
25 = 0.001 inch
We can say that 0.001 inch is the accuracy and least
count for type 2 of imperial Vernier Caliper.

13. For Further Information Related
to the Topic of Calculation of
Least Count
In Vernier Caliper