How do I sew a buttonhole and cut it open without ruining it?

Buttonholes intimidate people more than they should, largely because they are usually attempted for the first time on a finished garment where a mistake is expensive. The technique is mostly preparation: size it properly, interface it, and test it. The actual sewing is done by the machine.

What you'll need

• Interfacing appropriate to the fabric
• A seam ripper
• Two pins
• The buttons you will actually use
• Scrap of the same fabric for testing
• A fray-stopping liquid, optional

Step by step

1. Size the buttonhole from the button, not by eye.The length needs to be the button's diameter plus its thickness, plus about 3mm of ease. A thick or domed button needs noticeably more than a flat one of the same diameter. Measure with a tape wrapped over the button rather than guessing.
2. Interface behind every buttonhole.A buttonhole is a slit in fabric that is repeatedly pulled. Without interfacing it stretches, the stitching spreads and the edges fray. Fusible interfacing on the wrong side is enough on most garments; a firmer sew-in is better on knits and loose weaves.
3. Mark the position and the direction.Vertical buttonholes on a placket band, horizontal on a shirt front or a waistband where the button will be pulled sideways. The button sits at the end of the buttonhole nearest the garment edge, so the position of that end is what determines where the front edges meet.
4. Test on a doubled scrap with the same interfacing.Same fabric, same number of layers, same interfacing, same thread. Then check the button actually goes through it easily. This test is the whole job — everything after it is repetition.
5. Let the machine do it.A one-step buttonhole foot holds the button in a carrier at the back and sizes the hole automatically. A four-step foot is worked through the stages with a dial. Either way, follow the manual for your machine rather than a general description.
6. Stabilise the fabric underneath if needed.A layer of tear-away stabiliser or even tissue paper under a light fabric stops the dense satin stitching pulling it into a tunnel. Tear it away afterwards.
7. Seal the opening before cutting, on fraying fabric.A thin line of fray-stopping liquid down the middle of the finished buttonhole, left to dry, keeps the cut edges intact. Test it on a scrap first — some fabrics darken.
8. Cut it open with pins as stops.Push a pin across the buttonhole just inside each bar tack at the ends. Then insert the seam ripper in the middle and cut towards one pin, turn the work, and cut from the middle to the other pin. The pins physically stop the blade running through the end of the buttonhole, which is the mistake everyone makes once.
9. Check the fit and finish.The button should pass through with a little effort and not fall through. Trim any loose threads at the ends with small scissors rather than pulling them.

Tips

• Sew all the buttonholes on a garment in one session with the same settings. Machine buttonholes vary slightly with speed and thread tension, and a set sewn together looks consistent.
• Mark buttonhole positions from the finished garment rather than the pattern if the length has been altered — spacing them evenly along the actual placket looks better than following marks made for a different length.
• A buttonhole chisel and a small cutting block is the professional tool for opening buttonholes and gives a much cleaner cut than a ripper if you make a lot of them.
• On a thick or textured fabric a corded buttonhole — where a fine cord is laid under the stitching and drawn up afterwards — gives a much firmer edge.

Common mistakes

• Cutting without pins as stops — A seam ripper runs easily. One slip goes straight through the bar tack at the end and out into the garment, and there is no invisible repair for that.
• Skipping the interfacing — The buttonhole is under repeated strain every time the garment is fastened. Without interfacing it stretches out of shape within weeks and eventually tears.
• Making the buttonhole exactly the button's diameter — It has to pass the thickness of the button through as well as the diameter. A hole sized only on diameter will not do it up, or will do it up so tightly the fabric distorts.
• Testing on a single layer of scrap — A buttonhole in a placket goes through two or three layers plus interfacing. The machine behaves differently and so does the sizing.

If it doesn't work

Questions people ask