Vernier caliper reading practice
To read a vernier caliper, take the last main scale line at or before the vernier zero, then add the value of the one vernier line that lines up exactly with a main scale line. Each vernier line is worth the caliper's resolution, such as 0.02 mm or 0.001 in.
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Your reading
Right: 0 of 0
How to read a metric vernier caliper
The main scale is graduated in millimeters and numbered every 10 mm. On a 0.02 mm caliper the vernier has 50 divisions in the length of 49 mm, so each is 0.98 mm long, 0.02 mm short of a millimeter. Its numbers 1 to 10 mark tenths of a millimeter. A 0.05 mm caliper usually has 20 divisions in 39 mm, each 0.05 mm short of 2 mm. Calipers in school labs often read to 0.1 mm, with 10 vernier divisions in 9 mm.
- Read the last millimeter line on the main scale at or before the vernier zero.
- Find the vernier line that lines up exactly with a main scale line.
- Count its divisions from the vernier zero, multiply by the resolution and add the result.
Example on a 0.02 mm caliper: the vernier zero has passed the 28 mm line, and the line 9 divisions along lines up. The reading is 28 + 9 × 0.02 = 28.18 mm.
How to read an inch vernier caliper
On a 0.001 in caliper the main scale is graduated in steps of 0.025 in, with the inches and tenths numbered. The vernier has 25 divisions, and each vernier line adds 0.001 in.
- Read the inches and tenths at or before the vernier zero.
- Add 0.025 in for each further line up to the zero.
- Add the number of the vernier line that lines up, in thousandths.
Example: the vernier zero is two lines past 1.300 in, and vernier line 13 lines up. The reading is 1.300 + 0.050 + 0.013 = 1.363 in.
Common reading mistakes
Counting the main scale line after the zero
Use the last main scale line at or before the vernier zero. When the zero sits just short of a line, that line does not count yet, and the vernier shows a high value such as 0.98 mm.
Reading the nearest number
On fine verniers the numbers mark only some of the lines: tenths of a millimeter, or every fifth line on an inch vernier. Find the line that lines up and count the divisions to it from the nearest number.
Taking a line next to the aligned one
On a fine vernier the lines beside the aligned one miss by only one step, 0.02 mm on a 0.02 mm caliper. Take the line where its neighbors miss by the same amount in opposite directions.
Parallax
The vernier sits a little above the main scale. Manufacturer instructions say to look straight at the vernier line you check, because from an angle a different line seems to line up.
Zero error
Manufacturer instructions ask you to close the jaws and check that the vernier reads zero before use. If it still misses after you wipe the jaws, each reading is off by that amount: a caliper that shows 0.04 mm with the jaws closed reads 0.04 mm high.
Common questions
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How do you read a vernier caliper in mm?
Read the last millimeter line on the main scale at or before the vernier zero. Then find the vernier line that lines up with a main scale line and add its divisions times the resolution, for example 28 + 9 × 0.02 = 28.18 mm.
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What is the least count of a vernier caliper?
It is the value of one vernier division: the main scale division divided by the number of vernier divisions. A 50-division vernier on a 1 mm main scale reads to 0.02 mm, and a 25-division vernier on a 0.025 in scale reads to 0.001 in. The 10-division vernier of a school lab caliper reads to 0.1 mm.
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How do you read an inch vernier caliper?
Read the inches and tenths at or before the vernier zero and add 0.025 in for each further line. Then add the number of the vernier line that lines up in thousandths, for example 1.300 + 0.050 + 0.013 = 1.363 in.
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Why do two vernier lines seem to line up?
The lines beside the aligned one miss by only one resolution step. Take the line where its neighbors miss by the same amount in opposite directions. When the vernier zero sits exactly on a main scale line, the first and the last vernier lines both line up and the vernier adds nothing.
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How do you check a vernier caliper for zero error?
Wipe the jaws, close them and check that the vernier zero lines up with the main scale zero. If it does not, each reading is off by the same amount, so have the caliper checked or adjusted before you rely on it.
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