Picture of DIY Digital Caliper Micrometer Comparator
Get precise measurements with a cheap desktop scanner.

Using free software, you can measure part sizes with a resolution of less than a mil ( 1/1000 inch or about 25 microns ).

Great for identifying mystery micro-screws, electronics, camera parts, or even measuring plants or insects.

Tips and tricks for mounting parts, scanning, aligning the image, and taking measurements.

I'll give you links to other resources where people are using scanners for measurements and would like to hear from you about any ideas or feedback on how to get better results.

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Step 1: Free Software for Measurement

Picture of Free Software for Measurement
You can use nearly any graphics software for taking measurements.

The Notes and Resources step of this instructable gives links to notable image measuring software. Three free choices are IrfanView, The GIMP, and ImageJ. All are easy to use for basic measurements.

For simple measuring of lengths,  I prefer IrfanView graphics software.

Keep in mind that The GIMP is excellent and is my main image editor. It is worth your time to learn it as a free alternative to Photoshop.

ImageJ is a scientific and math miracle. Easy to use, but loaded with incredible features. Thanks to i'bler aman0311 for suggesting this.


IrfanView is Windows-only freeware. It is easy to load and use. It is kept up-to-date by its author Irfan Skiljan.

Be sure to download it from the official site IrfanView or from a trusted site like C|Net or tucows.

It installs quickly and easily. It's very light on resources, and is easy to learn.

Step 2: The GIMP

Picture of The GIMP
The GIMP is another favorite Open Source Freeware graphics program useful for measuring.

It runs on Windows, Mac, or Linux.

It's very powerful, and for basic measuring is easy to use, though not as simple as IrfanView.

You can download the GNU Image Manipulation Program from the official GIMP site or from C|Net and other trusted sources.

You can also use Photoshop, Picasa and many other programs to directly measure scanned parts.

Light_Lab1 year ago
I can recommend this technique, we have used it in the lab for about 20 years. The first time I used it was to measure thin flexible polymer sheet that was impossible to measure accurately any other way.
We never rely on firmware interpolated resolutions though, we always work at the fundamental mechanical resolution of the scanner. We also check the scanner by scanning an engineers steel rule. We have found the occasional scanner firmware interpolation that is inaccurate, and some cheaper scanners that have inaccurate DPI in their mechanics, sometimes they are non-linear.
It seems that the more expensive scanners are the most accurate and precise, we currently use an Epson V700 with a transparency back (highly recommended) to get 6400dpi, that is ~4 micron per pixel; so you can get ~25 pixels across the average width of a human hair.
Currently it is used to measure experimental soft contact lenses under development.
petr77 Light_Lab2 months ago

Would not taking a digital picture with say a smartfone (decent quality, rigged to a microscope perhaps) achieve the same or better results than with a scanner?

aman03114 years ago
flattness is an issue, but can be measured by acquiring an image of a known square object, and then drawing a straight measurement line from one sode of the object to another. Bottom line is this boils down to the quality of the optics used in acquisition. Shooting from farther away past a certain point (usually the lahf-way travel through a typical zoom lens) won't improve things. Basically take any lens assembly, set it at it's half-power point, and back up until you can focus in the midrange of the focusing system. Once there your in the best spot to acquire.
 very nice. Ive been needing a caliper. this will work in a pinch but i really need to go to the science and surplus store and get a real one
kelseymh5 years ago
What a really fascinating application of image software!  And for people who already own an "all-in-one" printer, much cheaper than buying precision machine tools :-)  Well documented as well.
iectyx3c (author)  kelseymh5 years ago
Thanks kelseymyh. Probably everyone already knows how to do this. I should try googling for photogrammetry and scanner to see what others have done.  I imagine there are better ways than my cheap and cheerful tip.
I doubt it.  If you're in a heay technical field where metrology is crucial (building silicon-based particle physics detectors, for example), then maybe it's obvious. 

If you asked the 20,000+ members of I'bles about it, I'd say there might be a few hundred who knew about the concept, and maybe a couple of dozen who could figure out how to make it work.

Your I'ble is a great introduction to a very sophisticated subject.
isacco5 years ago
Congratulations for this Instructable! It is useful and well explained.
The idea is simple and smart. It is not a real novelty, but the scanner calibration is a good idea for non flat objects.
I am in the research field and scanning flat objects (examples, leaves or plant roots) for automatic measurement is a usual task. Specialized software are available for this, both licensed and freeware.
A very good free software for complex measurement on digital images is ImageTool

aman03115 years ago
You can also use the NIH freeware that runs on Java called ImageJ. We use this frequently in microscopy.

Image J can perform calibrated measurements both hand-drawn as well as morphometric measurements (like mean feret, max/min, area, stuff like that). 

Finally the technique you used to calibrate can also be used with any digital camera. Simply take a picture of a known standard, find the pixel calibration, don't move the subject to camera distance and you can smap + measure away. This is best done using an improvised copy stand.

iectyx3c (author)  aman03115 years ago
Thanks aman0311 for the very useful ideas. Thanks to you, I am exploring the simplicity and power of ImageJ. I have added it to my list of favorite measurement software with a link to you for credit. ImageJ is an entire scientific toolbox of learning and is very impressive. I am grateful to you for telling me about it. I also like your camera calibration method and will try it out. I imagine that zooming in from a long distance probably gives the flattest image for measuring?
That seems to be very useful. And it's FREE! What could be better?
iectyx3c (author)  LuminousObject5 years ago
I think lots of people must already do this. I just find it to be a quick way to measure parts. If you guys find any i'bles or web sites already about this, please post them here and I will link to them. Thanks.
Ninzerbean5 years ago
I have no need for this but it was a really fascinating 'ible to read, thank you for sharing your knowledge. It's funny but the title is what made me what to know more.
iectyx3c (author)  Ninzerbean5 years ago
Thanks for your comment - yeah, I love browsing and reading i'bles in areas totally foreign to me, like sewing, cooking, or whatever, because I get ideas for my projects. i'bles is a great creativity booster.
Trebawa5 years ago
Idea: if the object is static, scan it a few times and combine them in the GIMP to eliminate the effects of noise and hopefully improve the (effective) resolution.
iectyx3c (author)  Trebawa5 years ago
Smart idea. Thanks for suggesting. Definitely would work.