Convert 40 mm to um

How to convert millimeters to micrometers

1. Formula: micrometers = millimeters × 1,000
2. Put in the value: 40 millimeters.
3. Result: 40,000 micrometers.

Millimeters to micrometers table

Converting the other way: micrometers to millimeters

millimeters = micrometers × 0.001. So 40,000 micrometers is back to 40 millimeters; one micrometer is 0.001 millimeters. See the micrometers to millimeters table.

Quick estimate in your head

For a rough answer, multiply by about 1000: 40 × 1000 ≈ 40,000 um, against the exact 40,000 um (0.0% out). Good enough to check that a calculated result is sensible.

Common mistakes

The usual slip is using the factor the wrong way round. A millimeter is bigger than a micrometer, so the number of micrometers must come out larger than the number of millimeters. If your answer goes the other way, divide instead of multiplying.

About the units

Millimeter (mm) and micrometer (um) are both units of length. One millimeter equals 1,000 micrometers, and one micrometer equals 0.001 millimeters. Results on this page are rounded for display; the conversion itself uses the exact definitions.

Length conversions come up in DIY and building plans, running and cycling distances, maps, clothing sizes and travel between countries that use metric and imperial units.

40 millimeters in other units

The most readable unit for this amount is inches (1.574803).

• 4 cm
• 0.04 m
• 0.00004 km
• 1.574803 in
• 0.1312336 ft
• 0.04374453 yd
• 0.00002485 mi
• 0.0000216 nmi
• 0.02187227 fm
• 40,000 um