Online RulerHow to measure button diameter
Measure a round button straight across its face, from outer rim to outer rim through the center. A line off to one side of the center gives a shorter reading. If the button is oval or irregular, record its widest span and the width at a right angle to that span.
- The diameter follows a straight line across the button's round outline.
- Use the outside rim, including a raised border when it forms the outside edge.
- The holes and the shank are separate features you can measure if they matter for a replacement.
- Place the button where you can see the full rim. If it is sewn on, spread the fabric flat and move any folds away from the edge.
- Place a ruler across the face or hold it close above the button. Aim the scale through the center and line up zero with the near rim.
- Look straight down at the far rim and record where it crosses the scale. Include the unit and mark the reading as approximate if the edge falls between lines.
- Check the span again across a different part of the face, still through the center. If the readings differ, check whether the ruler shifted or the button has an oval outline.
Find the center
Start by looking at the outline of the rim. If the holes sit in the middle, they can help you aim the ruler. When the holes or the pattern sit off center, use the shape of the rim as your guide. Shift the ruler a little to either side while keeping the direction fixed. For a round button, the widest straight span in that direction passes through the center.
Work around a dome
A domed face can make a ruler rock or hide part of the rim. For a loose button, put it on a flat surface and set a straight piece of stiff paper against each side, with both pieces parallel. Let them just touch the widest edges. Measure straight across the gap at a right angle to the paper edges. Check that neither piece moves when you bring the ruler over.
Match a button
Measure an intact button from the same garment if the one you want to replace is missing or chipped. Write down the outside diameter and note whether the button has holes through the face or a shank on the back. If you have a possible replacement on hand, check how it passes through the buttonhole. The rim shape and thickness can affect how easily it goes through.
Do I include the raised rim?
Yes, use its outer edge if it is the widest part of the button. A line where the rim meets the center panel measures only the panel.
How do I measure an oval?
Measure end to end along its longest direction, then measure the width straight across at a right angle. Write down both values with the unit.
Can I use a ruler beside the button?
Yes. Use two parallel straight edges to carry the rim positions over to the scale. Check that the ruler crosses those edges at a right angle before you read the distance.