Buttonholes are essential for any crochet project that includes a button closure. Here are the steps and tips for learning to crochet a buttonhole.
How to Make a Buttonhole within a Single Crochet Row
The row in which you will make the buttonhole is done in single crochet. See these instructions for single crochet if you need a refresher on the technique. You will also use a chain stitch, which you can learn with this chain stitch tutorial.
For a small button, single crochet in each stitch until you are at the point where you want the buttonhole to be, do a chain 1, skip next stitch (leaving it unworked), single crochet in each stitch remaining in the row. On the next row, single crochet in each stitch until you reach the chain-1 space, single crochet in the chain-1 space, single crochet in each stitch remaining in the row.
For a larger button, single crochet in each stitch until you are at the point where you want the buttonhole to be, do a chain 2, skip 2 stitches, single crochet in each stitch remaining in the row. On the next row, single crochet in each stitch until you reach the chain-2 space, work 2 single crochet in the chain-2 space, single crochet in each stitch remaining in the row.
For an even larger button, add a chain as needed, when you are making the buttonhole.
Test Your Buttonhole for Size Before Finishing the Row
Test putting the button through the buttonhole before you finish crocheting that whole row. For example, after you've crocheted four or five stitches beyond the buttonhole chain, see if the button will go through the buttonhole you just created.
The buttonhole shouldn't be too loose. Otherwise, the button won't stay buttoned on the finished piece. If it's so tight that it won't fit through at all, that is obviously a problem. If it's very tight but you can get it through after a struggle, you probably want to try again.
If it's not the right size for the button you're using, pull the crochet stitches out to the point where you began the buttonhole chain and adjust the number of chains that you used to make the buttonhole, so that it will fit the size button you're using. It's easy enough to pull a few crochet stitches out at this point and redo them, as needed, to help ensure that you will be happy with the final result on the entire finished piece.
After crocheting buttonholes a few times, you'll find that it becomes easier to judge the number of chains that you will need in any given buttonhole for the size button being used. You will also learn how tight or how loose of a buttonhole will work on your finished pieces.
Finishing and Reinforcing a Crocheted Buttonhole
If you wish to reinforce the finished buttonhole, you can work a round of slip stitch around the buttonhole opening to give it some firmness.