How do I convert µm to mm?

Use the formula shown above or enter a value to see µm converted to mm instantly.

What is the formula for µm to mm?

The converter calculates mm by applying the category-specific conversion factor for Length.

When should I use µm vs mm?

µm and mm are both part of the Length category; pick the unit that matches your measurement context (e.g., scale, region, or industry standard).

Length Converter & Reference

Convert µm to mm

Use the live converter below to translate between Micrometer (µm) and Millimeter (mm). Scroll further for quick examples, formula tips, and related units.

Formula insight: Most unit conversions use a simple multiplication or division by a conversion factor. The calculator shows the exact formula used.

Convert

µm → mm

Micrometer

µm

Millimeter

0.001

Rounded result (4 decimals max)

Formula

1 µm = 0.001 mm

Conversion sourcesTap or click to view references

The International System of Units (SI) — NIST Special Publication 330
National Institute of Standards and Technology (NIST). The SI Brochure (SP 330) is the definitive English edition of the BIPM SI tables. NIST’s edition lists the official constants and conversion factors tying inch-pound units to SI, which SwapUnits applies for length, mass, temperature, pressure, volume, and related conversions. See /standards/nist-si-tenfold for the complete decimal multiple/submultiple table. View source · View SI table

Results update as you type. Swap the direction to convert back from mm to µm.

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µm to mm quick table

Multiply any row by the same factor to scale results. Use the converter above to enter exact values with your own units.

Micrometer (µm)	Millimeter (mm)
0.25 µm	0.0003 mm
0.5 µm	0.0005 mm
1 µm	0.001 mm
2 µm	0.002 mm
5 µm	0.005 mm
10 µm	0.01 mm
25 µm	0.025 mm
100 µm	0.1 mm

mm back to µm

Keep the reciprocal handy when double-checking calculations or undoing a conversion.

Millimeter (mm)	Micrometer (µm)
0.25 mm	250 µm
0.5 mm	500 µm
1 mm	1,000 µm
2 mm	2,000 µm
5 mm	5,000 µm
10 mm	10,000 µm
25 mm	25,000 µm
100 mm	100,000 µm

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