Reference Guides

How Big Is 1ÎŒm?

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When designers and manufacturing companies specify surface finishes more often than not we’re talking in micrometres (”m), but what exactly is a ”m?


1 ”m is 0.001mm or one thousandth of one millimetre.  In other words it is a very fine measurement and as such it can be hard to comprehend.  So the best way to understand it for many of us is to compare it to everyday things we’d know, such as a cigarette paper, human hair, paperclip wire or needle.



This image from our partners Haas illustrates how these items measure up and what a ”m equates to in comparison.   For more details on their range of machining centres please visit their website at:


In comparison to microinches (written as ”in or ””) 1 ”m = approximately 40 ””.  1 ”” being equal to one millionth of an inch (0.000001”).  (So a 15”m surface finish = 600”” and a 320”” surface finish = 8”m as examples of conversions).


To understand more about surface reading types and how they are calculated, please see our post on A Guide to Understanding Surface Roughness Measurement Types




Post written by

Stephen Lewis-Brammer

General Manager