Buttonhole Size Calculator
A button passes through on edge, so its diameter alone will not fit. A 1.5 cm button 0.3 cm thick needs 1.8 cm, plus 0.3 cm of ease, so you stitch 2.1 cm. Forgetting the thickness is the classic error: on a thin shirt button at 0.15 cm nobody notices, but a coat button can be over 0.5 cm thick and the hole comes out plainly too small. A ball button is governed by half its circumference instead: π × 1.5 ÷ 2 = 2.36 cm.
Your numbers
Buttonhole length
2.1cm
Length for a ball button
2.36cm
Formula
Buttonhole length = Button diameter + Button thickness + Buttonhole ease, Length for a ball button = π × Button diameter ÷ 2
An automatic buttonhole foot measures the real button, thickness included, so it usually lands close to this figure. Test it on a scrap of the same fabric anyway — interfacing and the number of layers move it by a couple of millimetres. A horizontal buttonhole should start 2–3 mm past centre front towards the edge, because the fastened button is pulled to that end of the hole and has to end up on centre front. On knits, cut 2 mm shorter than calculated and back the area with interfacing, because the opening stretches.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Button diameter (cm)The button's diameter seen from above, ignoring the shank. | 1.5 | 0.1 and up |
| Button thickness (cm)Thickness of the button; leave it out and the hole comes up short. | 0.3 | 0 and up |
| Buttonhole ease (cm)Clearance for the button to pass — 2–3 mm is enough. | 0.3 | 0 ~ 1 |
Step by step
Quick reference table
Results when only Button diameter (cm) changes and everything else stays put.
| Button diameter (cm) | Buttonhole length (cm) | Length for a ball button (cm) |
|---|---|---|
| 0.75 | 1.35 | 1.18 |
| 1.13 | 1.73 | 1.77 |
| 1.5 | 2.1 | 2.36 |
| 2.25 | 2.85 | 3.53 |
| 3 | 3.6 | 4.71 |
What each result means
| Result | At default values |
|---|---|
| Buttonhole length (cm)Length of buttonhole to stitch: diameter plus thickness plus clearance. | 2.1 |
| Length for a ball button (cm)Buttonhole length for a ball button, set by half its circumference. | 2.36 |
Common mistakes
An automatic buttonhole foot measures the real button, thickness included, so it usually lands close to this figure. Test it on a scrap of the same fabric anyway — interfacing and the number of layers move it by a couple of millimetres. A horizontal buttonhole should start 2–3 mm past centre front towards the edge, because the fastened button is pulled to that end of the hole and has to end up on centre front. On knits, cut 2 mm shorter than calculated and back the area with interfacing, because the opening stretches.
Glossary
- Button diameter
- The button's diameter seen from above, ignoring the shank.
- Button thickness
- Thickness of the button; leave it out and the hole comes up short.
- Buttonhole ease
- Clearance for the button to pass — 2–3 mm is enough.
- Buttonhole length
- Length of buttonhole to stitch: diameter plus thickness plus clearance.
- Length for a ball button
- Buttonhole length for a ball button, set by half its circumference.
Frequently asked questions
Q. How is Buttonhole Size Calculator calculated?
Buttonhole length = Button diameter + Button thickness + Buttonhole ease, Length for a ball button = π × Button diameter ÷ 2 — A button passes through on edge, so its diameter alone will not fit. A 1.5 cm button 0.3 cm thick needs 1.8 cm, plus 0.3 cm of ease, so you stitch 2.1 cm. Forgetting the thickness is the classic error: on a thin shirt button at 0.15 cm nobody notices, but a coat button can be over 0.5 cm thick and the hole comes out plainly too small. A ball button is governed by half its circumference instead: π × 1.5 ÷ 2 = 2.36 cm.
Q. Can you walk through an example?
With Button diameter 1.5cm, Button thickness 0.3cm, Buttonhole ease 0.3cm, the answer is Buttonhole length 2.1cm.
Q. What do I need to enter?
Enter Button diameter, Button thickness, Buttonhole ease. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Button diameter (cm) moves the answer to Button diameter (cm) 0.75 → Buttonhole length (cm) 1.35 and Button diameter (cm) 3 → Buttonhole length (cm) 3.6. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
An automatic buttonhole foot measures the real button, thickness included, so it usually lands close to this figure. Test it on a scrap of the same fabric anyway — interfacing and the number of layers move it by a couple of millimetres. A horizontal buttonhole should start 2–3 mm past centre front towards the edge, because the fastened button is pulled to that end of the hole and has to end up on centre front. On knits, cut 2 mm shorter than calculated and back the area with interfacing, because the opening stretches.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.