← AskMachinist · Guides · Calculator · 🔎 Search
How to Read a Metric Micrometer
Guide · Updated October 28, 2026
A standard metric micrometer has a 0.5 mm pitch spindle. One full thimble turn moves 0.5 mm, and the thimble has 50 divisions, so each line is 0.01 mm.
Check your mic
Verify readings against a metric gage block stack built with the free Gage Block Calculator.
Step by step
- Check zero: Close the faces (or use the 25 mm standard on a 25–50 mm mic) with the ratchet and confirm the thimble reads 0.
- Measure: Close on the part square, using the ratchet or friction thimble for steady force.
- Read whole millimeters: Read the last whole millimeter line visible above the sleeve datum line.
- Check the half line: If a half-millimeter line below the datum is visible past that mm line, add 0.50 mm.
- Read the thimble: Add the thimble line aligned with the datum line × 0.01 mm.
- Add vernier if fitted: On 0.001 mm mics, add the sleeve vernier line that aligns with a thimble line × 0.001 mm.
Worked example
Sleeve shows 12 mm, and a half-millimeter line is visible past it. Thimble line 36 aligns. Reading = 12 + 0.50 + 0.36 = 12.86 mm.
Another part: 7 mm, no half line showing, thimble at 8: 7 + 0.08 = 7.08 mm. The most common mistake is missing or adding the 0.5 mm, so always check whether the half line shows past the last whole mm.
Tips
- Inch micrometers read differently: how to read an inch micrometer.
- Zeroing: zeroing calipers and mics.
- Check accuracy across the range: how to check a micrometer with gage blocks.
- Metric stacks: metric gage block stacks.
- Vernier basics: how to read a vernier scale.
FAQ
How do you read a metric micrometer?
Whole mm on the sleeve, plus 0.5 mm if the half line shows, plus the thimble line × 0.01 mm.
How many divisions on a metric micrometer thimble?
Fifty, each worth 0.01 mm, because one turn moves 0.5 mm.
What is the resolution of a metric micrometer?
0.01 mm standard, or 0.001 mm with a sleeve vernier or digital readout.
How do I check a metric micrometer?
Measure metric gage blocks at several points across the range, such as 2.5, 5.1, 7.7, 10.3, 12.9, 15, 17.6, 20.2, 22.8 and 25 mm.
Is there a free gage block calculator?
Yes. The Gage Block Calculator at gageblockcalc.com builds any inch or metric stack, free with no login.
Related guides and calculators
- How to read an inch micrometer
- How to check a micrometer with gage blocks
- Metric gage block stacks
- Zeroing calipers and micrometers
- How to read a vernier scale
- How to Use a Depth Micrometer
- Inch and Metric Conversion for Machinists
- ISO 286 Hole-Basis Fits Explained (H7/g6, H7/h6, H7/k6, H7/p6)
- All free machinist calculators
Build your stack in seconds
The free Gage Block Calculator finds the fewest-block combination for inch and metric sets, with wear blocks. No login.
Questions? Ask a machinist.
General shop information only — follow your tooling, machine and gage manufacturers' instructions and your quality system.