Micrometers to MM Converter

Common questions

How many mm is 1 micrometer?

0.001 mm, because one thousand micrometres make a millimetre. The pattern holds at every size: 5 µm is 0.005 mm, 25 µm is 0.025 mm, 50 µm is 0.05 mm, 200 µm is 0.2 mm, 1,500 µm is 1.5 mm and 12,345 µm is 12.345 mm. The conversion moves the decimal point three places to the left, and the displayed result rounds longer inputs to twelve significant digits.

What is the formula for micrometers to mm?

Millimetres = micrometres / 1,000, and micrometres = millimetres × 1,000 in the other direction, so 2.5 mm is 2,500 µm. Micro is the SI prefix for a millionth of the base unit and milli for a thousandth, so a millimetre is one thousand micrometres by definition rather than by measurement. The factor carries no error, and any rounding you see comes from the display, which prints twelve significant digits and falls back to exponential notation below 0.000001.

Do I divide or multiply, and which way does the decimal point move?

Divide, and the point moves left by three places going from micrometres to millimetres: 8 µm becomes 0.008 mm and 450 µm becomes 0.45 mm. Multiply, and the point moves right by three places going the other way: 0.45 mm becomes 450 µm. The Swap units button between the two boxes reverses the pair, so this page turns into a millimetres to micrometres converter without a reload.

What is 70 micrometers in mm, and what else does the list show?

70 µm is 0.07 mm. The list under the answer holds the other length units at the same time, because the converter works out every common one at once rather than one target at a time. Type 100 in the From box and the headline reads 0.1 mm, with 0.01 cm, 0.0001 m, 1e-7 km, 0.00393700787402 in, 0.000328083989501 ft and 0.000109361329834 yd in the list below. Copy result copies the headline exactly as printed, without the thousands separators.

Is a micron the same as a micrometer?

Yes. Micron is the older name for the same unit, one millionth of a metre, so a 5 micron filter rating and a 5 µm filter rating are the same number and both are 0.005 mm. SI dropped the name in 1967 and kept the unit, which is why filtration, coatings and 3D printing still say microns while the symbol on a drawing is µm. In the From box here the unit is listed as Micrometre (µm); the arithmetic is identical whichever word you came for.

What is the difference between micrometres, millimetres and nanometres?

Each step is a factor of 1,000: 1 mm is 1,000 µm and 1 µm is 1,000 nm, so a millimetre is a million nanometres. That is where the common slip lives, since writing 100 mm when you meant 100 µm is a thousandfold error. One thou, the imperial neighbour also written mil, is 25.4 µm exactly. Nanometres and thou are uncommon units: both dropdowns always list them, and the uncommon units switch in the readout is what adds them to the list under the answer.

Why does the page open on µm and mm when I last converted something else?

Because a page that names a pair should show that pair. This one sets micrometres and millimetres on arrival, ahead of whatever the converter last remembered, and it leaves the main unit converter's own memory alone: go back there and it is still on the pair you left it on. The number you last typed does come with you, since it is usually the one you are still working on.