Have you noticed that your gauge tightens up when you knit in the round? If so, join the club! It’s very common for the knit st to be tighter than the purl st so when you eliminate the purl rows by knitting in the round you often tighten up significantly.
If you know you do this, you *should* work a swatch in the round before you begin a project. I am in the club and I know my gauge is tighter, but not dramatically different. So what I do is work a swatch flat, get it close or slightly on the large side, then begin my project in the round. After the first few rounds I measure my gauge and if it is way off, I go up a needle size. Usually by the time I’ve worked a few rounds I loosen up and it’s fine.
If you are working a garment such as Liesl or Gretel and you know your gauge is going to loosen up once you get to the armholes and begin working back and forth try this trick: use two different needles, the working size on knit rows and one size smaller on purl rows. If you have interchangeable needles it’s even easier, attach the smaller needle to the end that you’ll use for purl rows. Try it and see. If this takes care of your problem you may be able to knit flat swatches this way to get a good approximation of you circular gauge.