Do I need calipers to measure a part?

No. A ruler or tape measure is enough for most parts. Round to the nearest millimeter.

What if I cannot get an exact number?

Send your best estimate and say it is rough. A photo next to a coin or ruler helps fill in the gap.

Where do I put the measurements when I contact you?

Our request form has a field just for sizes. Fill in what you have there, even if it is only one or two numbers.

How do I measure a round part without calipers?

Measure straight across the middle with a ruler. If the part is small, wrapping a tape measure around it and dividing by about 3.14 also gets you close.

Does a rough measurement guarantee a perfect fit?

No. It gets us started. Anything with a tight tolerance, like a thread or a snug connector, usually needs a follow-up question before we can be sure.

Updated 2026-09-05 · 5 min read

How do I measure a replacement part?

Quick answer

Use a ruler or tape measure. Get the length, width, and thickness of the part, and the diameter of any hole or peg, to the nearest millimeter. Note which way is up and which side faces out. Lay the part next to a coin or ruler in a photo for scale. Rough numbers are enough to start, since a tight fit is checked with you before anything is printed.

Upload your file and get one printed for you.

You do not need a caliper or any special tool to measure a broken part well enough to describe it to us. A ruler, a tape measure, and a few careful numbers written down clearly get you most of the way there.

The numbers that matter most

Start with the three basics: how long the part is, how wide, and how thick. If it has a hole, a peg, or a screw post, measure across it too, since that is often the number that decides whether a replacement actually fits. Round to the nearest millimeter. You do not need more precision than that for us to start looking or start planning a remake.

Measuring something round

A round part, like a knob or a cap, is easiest measured straight across the middle, through the center point, rather than around the outside edge. If you only have a soft tape measure and the part is small, wrap the tape around the part to get the distance around it, then divide that number by about 3.14 to get the distance across. It will not be lab-perfect, but it gets close enough to start.

How to measure and describe your part

Step 1
Measure length, width, and thickness
Use a ruler or tape measure. Round to the nearest millimeter.
Step 2
Measure any hole, peg, or post
These small numbers often matter more than the overall size, since they decide whether the part actually seats correctly.
Step 3
Note which way is up
Say which side faces out, and which edge sits against something else. A word or two is enough: "the flat side goes against the wall".
Step 4
Take a photo next to something for scale
Lay the part next to a coin, a ruler, or a tape measure in the photo. This backs up your numbers if anything is unclear.
Step 5
Send it all in one place
Our request form has a spot for sizes, a spot for what the part does, and a spot for a photo. Fill in what you have.

Worth knowing

Where a home measurement runs out of road

A ruler measurement is not a lab measurement, and that is fine for most parts. It runs into trouble on anything with a tight fit, like a screw thread that has to match another part exactly, or a snug electrical connector. On those, a rough number is still a useful starting point, but expect a follow-up question or two before anything gets made, rather than an instant match.

Do I need calipers to measure a part?: No. A ruler or tape measure is enough for most parts. Round to the nearest millimeter.
What if I cannot get an exact number?: Send your best estimate and say it is rough. A photo next to a coin or ruler helps fill in the gap.
Where do I put the measurements when I contact you?: Our request form has a field just for sizes. Fill in what you have there, even if it is only one or two numbers.
How do I measure a round part without calipers?: Measure straight across the middle with a ruler. If the part is small, wrapping a tape measure around it and dividing by about 3.14 also gets you close.
Does a rough measurement guarantee a perfect fit?: No. It gets us started. Anything with a tight tolerance, like a thread or a snug connector, usually needs a follow-up question before we can be sure.

Don't have a file? Tell us what you need.

Common questions

Do I need calipers to measure a part?: No. A ruler or tape measure is enough for most parts. Round to the nearest millimeter.
What if I cannot get an exact number?: Send your best estimate and say it is rough. A photo next to a coin or ruler helps fill in the gap.
Where do I put the measurements when I contact you?: Our request form has a field just for sizes. Fill in what you have there, even if it is only one or two numbers.
How do I measure a round part without calipers?: Measure straight across the middle with a ruler. If the part is small, wrapping a tape measure around it and dividing by about 3.14 also gets you close.
Does a rough measurement guarantee a perfect fit?: No. It gets us started. Anything with a tight tolerance, like a thread or a snug connector, usually needs a follow-up question before we can be sure.

Ring, Nest, eufy, Blink, Wyze, eero, TP-Link, Netgear, ASUS, and Starlink are trademarks of their owners. We are not connected to those companies. We use the names only to say what things fit.