Buttonhole Size
Size a buttonhole from button diameter and thickness.
Across the face of the button.
Depth that must pass through.
1.188 in
About 30 mm from end to end.
- Diameter plus thickness
- 1 in
- Weight ease
- 0.188 in
- Cut / stitch length
- 1.188 in
The diameter-plus-depth rule works because the button must fold through the hole on a small shank, so the hole has to clear the whole depth, not just the face. Heavier cloth springs open more, which is why it takes the larger ease. Test on an offcut before cutting the garment itself.
About This Tool
The Buttonhole Size calculator works out how long to cut or stitch a buttonhole from the button itself, using the tailor's rule of diameter plus thickness, then a small ease chosen for the weight of your fabric.
You measure across the face of the button and through its depth.
It adds those together and layers on the ease a woven, medium or heavy cloth needs to spring open.
The answer ends the two classic failures of a hole too tight to button or too loose to hold.
A hole sized to the button, not to a chart, is what makes a handmade shirt feel store-finished.
It also warns that a thick shank button needs a longer opening than a flat one of the same width.
Getting one clean measurement means every buttonhole down the placket can copy it exactly.
Why Buttonhole Size Math Matters
A buttonhole must pass the whole depth of the button, not just its round face, to lie flat when fastened.
Cut too short and the button strains the hole, tearing the thread ends with daily wear.
Cut too long and the garment gapes between buttons, spoiling a carefully pressed front edge.
Heavier fabric springs the hole open further, so it quietly needs a longer ease than a light voile.
A shank or balloon button sits proud of the cloth and demands more length than a flat one.
Getting the first hole right lets you replicate it down a placket without re-measuring each time.
Buttonholes are the detail buyers notice, and a well-sized one reads as skilled handwork.
A wrong hole cannot simply be shortened again, so measuring once saves the whole front piece.
The Formula
The buttonhole length equals the button diameter plus its thickness, then a fabric-weight ease of about an eighth to a quarter inch, because the hole must clear the full depth of the button and still hold it snug once fastened.
- Diameter —
- the distance straight across the round face of the button
- Thickness —
- the depth the button must fold through when it passes the hole
- Ease —
- a small added length by fabric weight so the hole springs open without gaping
The ease is deliberately small, since the goal is a hole the button slips through with slight resistance rather than one that hangs open and shows the thread bar tack.
Worked Example: Step by Step
- 1You are making a shirt with flat buttons 0.75 inches across.
- 2Each button is 0.25 inches thick, so diameter plus thickness is a full inch.
- 3The cloth is a medium poplin, so the tool adds about three sixteenths of ease.
- 4That gives a finished buttonhole length of roughly one and three sixteenths inches.
- 5You mark and stitch a test hole on an offcut at that length first.
- 6The button passes with a firm snap and the front lies flat, so you set the machine foot to match.
- 7Every hole down the placket now copies the one proven measurement instead of a guessed number.
How to Use This Calculator
- Measure the button diameter straight across its face.
- Measure through the button to find its thickness.
- Pick the fabric weight to set the right ease.
- Read the recommended hole length in inches and millimetres.
- Test the length on an offcut before cutting the garment.
- Open a too-snug hole carefully with a stiletto rather than recutting.
- Copy the proven figure to every hole down the placket.
Key Terms
- Diameter
- the straight distance across the round face of a button
- Thickness
- the depth of a button that must fold through the finished hole
- Ease
- the small extra length added so a hole clears the button without gaping
- Shank button
- a button raised on a stem that needs a longer hole than a flat one
- Bar tack
- the short reinforced stitch at each end of a hand-worked buttonhole
- Bound hole
- a hole edged with bias binding instead of thread, common on soft fabrics
- Stiletto
- a pointed tool used to gently open a stitched hole without cutting its thread ends
Buttonhole Size Reference Table
| Fabric weight | Typical ease | Hole character |
|---|---|---|
| Light | about 1/8 in | Snug, low spring-back |
| Medium | about 3/16 in | Everyday shirt front |
| Heavy | about 1/4 in | Coat or outerwear |
The ease grows with fabric weight because thick cloth springs the hole open more than a thin voile ever will, so always cut on the smaller side and stretch the opening open with a stiletto only until the button passes with a firm snap rather than a loose gap.
Common Mistakes & Pro Tips
- Sizing the hole to the button diameter alone and forgetting the depth it must fold through.
- Using one flat-hole rule for a shank button, which then cannot pass the shortened opening.
- Cutting a heavy-coat hole with a light-fabric ease, so the fastening strains and tears at the ends.
- Skipping the offcut test and discovering a too-long hole gaping on the finished front panel.
- Measuring a decorative balloon button at its widest ornament instead of its passing face.
- Trusting a machine foot setting copied from a different thread weight without retesting.
Real-World Use Cases
- Sizing shirt-front holes before sewing a placket.
- Adjusting a pattern's given buttonhole for a thicker button.
- Working a coat hole that must clear dense wool.
- Choosing a hole length for a raised shank button.
- Teaching the diameter-plus-depth rule to a beginner.
- Sizing a cuff hole where a small button meets thick fabric.
- Matching new holes to buttons on a repaired garment.
Buttonhole Size: Frequently Asked Questions
Why add the thickness and not just the width?
A button folds through on its edge, so the hole must clear the full depth as well as the face. Sizing to the diameter alone leaves a hole the button cannot pass without tearing the ends.
How much ease does a thick coat need?
Around a quarter inch, since dense cloth springs the hole open more than a light fabric. The heavier the material, the longer the ease, so the tool raises it for coats and lowers it for voile.
Does a shank button change the length?
Yes, a shank button sits raised above the cloth, so it needs a longer hole than a flat button of the same face. Measure the part that passes through, not the widest ornament.
Should I test before cutting?
Always stitch a sample hole on an offcut of the same fabric and interfacing first, then pass the real button through it. A too-long hole cannot be shortened, so the scrap test protects the whole front panel.
Can I copy one length down a placket?
Once one hole fits with a firm snap, mark and stitch every other hole to that exact length so the front looks even. Consistent holes read as skilled work, while a drifting length makes a shirt look untidy.
This page explains how the buttonhole size works, what each input means and where the numbers come from, so you can plan your next make with confidence.
Written by Bobbin & Form Editorial Team
Home sewists & machine-embroidery practitioners
Reviewed by Marie Delacroix
Custom sewist & machine-embroidery technician, 15 years at the machine
Formulas follow standard sewing and needlework references. Results are estimates — always confirm against your pattern and a pre-washed swatch.
Sources & further reading
- Threads Magazine — fabric cutting & yardage guides
- ISO 13934 — textile tensile & fabric property standards
- Your local fabric store's bolt-width charts