Pattern call for 16 gauge yarn

Hello-I could just kick myself! I just bought yarn that knits at 21 to make a sweater for my DH. I felt a bit unsure about the pattern I choose, it’s a DROPS pattern and I’m finding it difficult to understand, anyway, then I went to my LYS and found a Knitting Pure and Simple pattern (I’ve use their patterns before with great success) but it calls for 16 sts to the inch and I just spend a tiny fortune on yarn for his sweater that knits at 21. Is there anyway I can use the yarn I already have or do I have to just add it to my stash and start over with a yarn that knits at 16??? BTW, the pattern is #264 adn it’s a Neckdown Cardigan for Men and I plan on making a buttonband, not putting in a zipper at the picture shows, for those of you who are familiar with this particular pattern. Thank for your help!

First, try using a larger needle and see if you can get 16 sts/4". You probably can, but it may be knit a lot looser than you like. So find a needle that gives you somewhere between 18 and 20 sts per 4" or whichever gives you a fabric you like. Then divide the sts per inch into the sts for a larger size of the pattern and decide if that’s going to give you the finished measurement you need, or close to it.

The Knitting P & S patterns are all top down, so you can adjust them easily anyway. Cast on a couple sizes larger and do the increases until the back sts are half the chest size you want including a couple inches for ease. Then separate off the sleeve sts and finish the body, then work on the sleeves. The lengths are given in measurement so you need the body and sleeve length to be what would be his normal size. The only problem you might run into is that you need more yarn, but if you got enough for one his size anyway at the smaller gauge, you could be okay.

Thank you very much! Your suggestions, advice are great and I’ll do as you’ve said and see what happens. If all else fails, I can buy more yarn…