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How to Read an Inch Micrometer
Guide · Updated October 27, 2026
A standard inch micrometer reads to 0.001 in on the thimble, and to 0.0001 in with a vernier. Add the values up in this order.
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Step by step
- Sleeve numbers: Each numbered sleeve line is 0.100 in.
- Sleeve lines: Each small line between the numbers is 0.025 in.
- Thimble: Each of the 25 thimble divisions is 0.001 in. Read the line that's on the sleeve index.
- Vernier: On a tenths mic, find the vernier line that aligns. Each is 0.0001 in.
- Add: Example: 0.200 + 3 × 0.025 + 0.012 = 0.287 in.
Tips
- Use the ratchet for consistent force.
- Zero the mic first: how to zero.
- Check a reading on a gage block.
Related: vernier scales, checking a micrometer.
Quick shop check
Example reading: sleeve shows 0.300 in plus two lines (0.050 in) = 0.350 in; thimble at 12 = 0.012 in; vernier line 3 = 0.0003 in. Total = 0.3623 in. Check zero on a 0–1 in mic by closing the faces with the ratchet.
FAQ
How do you read a micrometer?
Sleeve numbers (0.100) + sleeve lines (0.025 each) + thimble (0.001 each) + vernier (0.0001).
What is each thimble line worth?
0.001 in. There are 25 per revolution, and the spindle pitch is 40 TPI.
How do I read tenths?
Find the vernier line on the sleeve that aligns with a thimble line. Its number is the tenths.
How do I check my readings?
Measure gage blocks. Build any reference size free with the Gage Block Calculator at gageblockcalc.com.
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General shop information only — follow your gage manufacturer's instructions and your quality system.