Mixing RAM sizes is fine, but you'll probably lose dual-channel.

Yes, you can mix a 16GB and a 32GB stick. Most modern motherboards handle it (especially with Intel’s Flex Mode or AMD’s similar logic). You’ll get 48GB total, and it’ll work.

The main catch is dual-channel memory. If you have two sticks of different capacities, the system usually runs the first 32GB (16+16) in dual-channel and the remaining 16GB in single-channel. That means some operations see a small performance hit—maybe 5–10% in memory-heavy tasks like video editing or gaming. For everyday browsing or office work, you won’t notice.

Other risks: mismatched speeds or timings. If your 16GB stick is faster, the system will throttle both to the slower stick. And if one stick is finicky (e.g., different die type or voltage), you might get random crashes. But if you buy sticks from the same manufacturer or at least the same speed rating, chances are good.

I do this myself. It’s not ideal, but it’s practical if you have the spare stick and don’t want to buy a matched pair. Just run a memory test (like MemTest86) afterward to be sure.