Swap your 2x8GB for 2x16GB.

Yes, you can, but you have to replace the sticks, not add more. Since all slots are full, you’d pull out the old 8GB sticks and put in two 16GB sticks. That gives you 32GB total.

Make sure your motherboard supports 32GB (most modern ones do at 3200MHz or whatever your CPU likes). Check the QVL for your board if you want to be safe, but honestly any decent brand kit will work.

One gotcha: mixing different RAM kits is a gamble. So don’t try to keep one 8GB stick and add a 16GB stick — that’ll run in odd dual-channel mode and likely cause stability headaches. Just buy a matched 2x16GB kit and be done with it.

Future-proof tip: if your board has four slots and you can find a 2x16GB kit now, that leaves two slots open for later. But you said all slots are full, so I’m guessing you’ve got two slots and that’s it.