Calipers have a bit of a reputation for being intimidating. It’s not obvious how to use them, or how to read them, and their name isn’t a basic vocabulary word (so don’t feel bad if you didn’t now what they were) – BUT they’re possibly the most important tool to have.

Calipers can measure the width of anything smaller than they are with incredible accuracy. For jewelry making, they’re used to measure beads, bore holes, jump rings, and wire and cord gauges.

Most beads are measured using the metric system, which is why we sell all our beads by the millimeter (mm). Our strands of rounds come in 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, and 16 mm, but the more odd shaped strands vary from bead to bead. Knowing the width of your project can help with the design or construction s well as help our staff find you exactly what you are looking for. Knowing the bore hole size can save you hours of time trying every size of wire to find the perfect match.

Here is a quick guide on reading calipers.

Outside Calipers

To measure the width of an object:

1. Line up the bead in the jaws of the calipers so the bore hole is parallel with the jaws. This way, you’re measuring the width of your finished project instead of the length of the bead. If it’s a round, it doesn’t matter which way you turn it since it’s a circle.
2. Close the jaws on the bead. You want to be able to pass the whole bead between them, so they should slide over the edges without catching.
3. This is the hard part. There are two edges to calipers, one metric and one imperial. You want the metric side, that way everything is in the same unit. There’s the main body with however many centimeters (cm) to the edge of the tool, and the slider with 1 cm on the metric side and a mark on the imperial. Look at the slider and find the edge of the 1 cm closest to the bead, then see where that lines up on the main body. The mark just before the slider’s is how wide the bead is, rounding down to the nearest millimeter.
4. If you want to get more specific, see which mark on the slider matches perfectly with the marks on the body. In the image below, the bead is 14 mm. If you want to be more specific, find the second mm mark on the body that lines up with one on the slider. This Labradorite bead is 14.1 mm wide.

It will take a bit of practice to instantly read calipers, but it’s well worth it for sorting that random drawer we all know you have. It’s all right, we have all have one, too.

This technique will work on anything, from measuring wire to nails to knitting needles.

Inside Calipers

You measure the bore hole just like measuring the outer width of a bead. Line up the inner edges of the jaws with the edges of the bore hole and take your reading. If your caliper has two sets of jaws, use the ones that have the flat edges facing away and put them into the bore hole.

Usually you only need to do this to make sure your beads will fit a certain size elastic or cord. Nothing is worse than finding out your cord is far too big for your beads after you’re home for the night, and using calipers to check is a quick way to make sure that doesn’t happen.