Micrometers to Inches Converter
An inch is exactly 25.4 millimetres, which makes it exactly 25,400 micrometres, so micrometres to inches is one division: inches = µm / 25400. That puts 1 µm at 0.0000393700787402 in, 25.4 µm at exactly 0.001 in, 100 µm at 0.00393700787402 in, 500 µm at 0.0196850393701 in, 12,700 µm at exactly 0.5 in and 25,400 µm at exactly 1 in. Micron is the older name for the same unit, so a 5 micron rating converts identically, to 0.000196850393701 in. The 25.4 is a definition from the 1959 international yard and pound agreement rather than a measurement, but the decimal it produces repeats, so answers print to twelve significant digits and fall back to exponential notation below 0.000001: 0.02 µm reads 7.874016e-7 in. This page opens the converter with Micrometre (µm) in the From box and Inch (in) in the To box, whatever pair you converted last, and the list under the answer carries the same length in millimetres, centimetres, metres, kilometres, inches, feet, yards, miles and nautical miles.
1 µm in every length unit
Common questions
- How many inches is 1 micrometer?
- 0.0000393700787402 in, which is 1 divided by 25,400. The digits repeat at every size and only the decimal point moves: 10 µm is 0.000393700787402 in, 100 µm is 0.00393700787402 in, 1,000 µm is 0.0393700787402 in and 1,000,000 µm is 39.3700787402 in. Going the other way, 25,400 µm is exactly 1 inch and 12,700 µm is exactly half of one.
- What is the formula for micrometers to inches?
- Inches = micrometres / 25,400, and micrometres = inches × 25,400 in the other direction, so 0.5 in is 12,700 µm and 2 in is 50,800 µm. An inch has been exactly 2.54 centimetres since the 1959 international agreement on the yard and the pound, and micro is the SI prefix for a millionth, so 25,400 µm to the inch is a definition that does not drift with time or country. Dividing by that exact figure is why 25,400 µm comes back as 1 and not as 0.99999. The Swap units button between the two boxes reverses the pair, so this page turns into an inches to micrometres converter without a reload.
- How do I convert microns to thou or mils?
- Divide by 25.4, because one thou is a thousandth of an inch and therefore exactly 25.4 µm. So 25.4 µm is 1 thou, 100 µm is 3.93700787402 thou and 1 µm is 0.0393700787402 thou. Thou, written mil on many drawings, is one of the uncommon units here: both dropdowns always list it, and the Uncommon units switch in the readout, labelled Show 7 more, is what adds it to the list under the answer along with nanometre, furlong, astronomical unit, light year and parsec.
- Is a micron the same as a micrometer?
- Yes. Micron is the older name for one millionth of a metre, so a 5 micron filter rating and a 5 µm rating are the same number, both 0.000196850393701 in. SI dropped the name in 1967 and kept the unit, which is why filtration, coatings and 3D printing still say microns while a drawing carries the symbol µm. In the From box here the unit is listed as Micrometre (µm), and the arithmetic is identical whichever word you came for.
- Is the decimal exact, or is it rounded?
- The definition is exact; the decimal is not. One micrometre is 1/25400 of an inch, and 25,400 factors into 2, 5 and the prime 127, so the decimal never terminates: 0.0000393700787401574... The page rounds at twelve significant digits, which is well inside what double precision carries, and prints 0.0000393700787402. Lengths that land on a round inch figure come back exact instead of as a trail of nines: 25.4 µm gives 0.001 in, 254 µm gives 0.01 in and 25,400 µm gives 1 in.
- What is 100 microns in inches, and what else does the list show?
- 100 µm is 0.00393700787402 in, just under four thou. The list under the answer holds every common length unit at the same time rather than one target at a time, so the same 100 µm also reads 0.1 mm, 0.01 cm, 0.0001 m, 1e-7 km, 0.000328083989501 ft and 0.000109361329834 yd. The From box accepts a typed exponent and thousands separators, so 2.54e4 and 25,400 are both read as 25,400 µm. Copy result copies the headline exactly as printed, without the separators.
- Where does a micron to inch conversion come up?
- Machining tolerances and surface finish, coating and film thickness, filter ratings and 3D printer layer heights are quoted in microns in metric shops and in thou or decimal inches in imperial ones, so the same part gets described both ways. A 50 µm layer height is 0.00196850393701 in, just under two thou. A 2.5 µm surface finish is 0.0000984251968504 in, and a human hair at roughly 70 µm is 0.00275590551181 in.
- Why does the page open on µm and inches when I last converted something else?
- Because a page that names a pair should show that pair. This one sets micrometres and inches 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.
Conversion factors are the exact legal definitions where one exists. An inch is exactly 2.54 cm and a pound exactly 0.45359237 kg, so those conversions are exact rather than approximate. Temperature uses offsets rather than factors, and that is shown in the working.