Mixing RAM sticks usually works.

Probably. But “usually” and “works” have some caveats.

When you mix a 16GB stick with two 8GB sticks, dual-channel will generally still engage, but it runs in what’s called “flex mode” or “asymmetric dual channel.” The first 16GB (the 8+8) runs dual-channel, and the extra 8GB (the leftover on the 16GB stick) runs single-channel. For most gaming and everyday use, you won’t notice a difference. Benchmarks might show a small dip, but real-world impact is usually under 5%.

The bigger risk is compatibility—mixing different brands or speeds can cause instability. If the new stick is the same brand and speed (or at least same speed and timings), you’re fine. If they’re mismatched, you might get crashes or a forced downclock to the slower speed.

Worst case, it doesn’t boot. Best case, you get 32GB and save money over buying a matched kit. I’d try it. You can always return the stick.