The Cult of Cars, Racing and Everything That Moves You.
We may earn a commission from links on this page

The Humble Digital Caliper Takes The Guesswork Out Of Precise Measurements

This cheap tool has so many uses around the home or in the shop.

We may earn a commission from links on this page.
Image for article titled The Humble Digital Caliper Takes The Guesswork Out Of Precise Measurements
Screenshot: Dan Reed / Jalopnik

Over the past few weeks we’ve looked at the rivet nut, a little fastener that creates a nice, threaded hole where once there was only misery, a ratcheting brake caliper piston spreader, a tool that’s better at the job of spreading brake caliper pistons than a C-clamp and an advanced diagnostic scanner for deep down diagnostics. This week’s cool tool is the humble digital caliper, a tool that makes measuring easy, if not fun.

This suggestion comes from our own Raphael Orlove, and he adores how cheap and useful these tools are.


Car repairs, maintenance and upgrades sometimes involve getting accurate measurements. If you drive a car with limited parts availability, you may have to get creative and find an off-of-the-shelf part that does or can be made to do the job. But getting there, or even making your own parts will require you to get some measurements.

It’s easy to just pull out a ruler or tape measure or eyeball something, and sometimes you’re working with a part where such a method of measurement works just fine. A good example of this would be exhaust pipe diameter. Being off by a couple of millimeters isn’t the end of the world, here.


But there are plenty of situations where a measuring tape just isn’t going to cut it.

This is where a caliper can come in. Its uses go about as far as your imagination does. Use a caliper to measure clearances in bearings, brake rotor thickness, thread pitch, thread depth, cylinder diameter and more. A caliper can even be used to check for play in parts like a steering wheel and ball joints.

These tools are cheap, but how they work is pretty cool. A digital caliper uses capacitance to give you a measurement reading. The caliper uses sensors to detect changes in electrical charge based on how far the jaws are apart. Part of the magic is a number of engraved plates under the scale that form an array. As the jaw slides across the scale, those plates underneath align and misalign with the jaw, changing the capacitance and the measurement reading. The result is accuracy down to about 0.001-inch for high-quality calipers.

Check out this handy video by YouTuber Dan Reed on a neat trick to use a digital caliper to measure rotor thickness:

Cheap digital calipers run as low as $9 on sites like Amazon, but beware, as cheaper calipers may have poorer accuracy than a model designed for professionals.


One well-reviewed example is the $184 Mitutoyo 500-196-30CAL. This monster digital caliper comes with a certified accuracy of plus or minus 0.001-inch. For jobs where accuracy is of the utmost importance, it pays to get get a more expensive model.

Do you know of a weird or unique but must-have tool that every wrencher should have? Do you want to see us put a type of tool to the test and see how it performs? Shoot me an email or drop it down in the comments!