16GB is worth it for that PC.

Yes. If you regularly have dozens of browser tabs open alongside Word, Excel, and maybe a PDF reader, 8GB is probably your bottleneck. The i5-2400 is old but still fine for office work — the problem isn’t the CPU, it’s running out of RAM and hitting the page file.

Chrome or Edge alone can eat 4–6GB with a bunch of tabs. Add Office apps and background stuff, and 8GB gets tight. You’ll notice stuttering, lag when switching tabs, or the whole machine slowing down. Doubling to 16GB gives you headroom so the system doesn’t have to swap memory to your hard drive constantly.

The upgrade is cheap — used DDR3 sticks are a few bucks on eBay. Just make sure your motherboard has two free slots and you match speeds (or run mismatched sticks in flex mode). It’s probably the best performance-per-dollar upgrade you can do on that machine.

If you only have 4–5 tabs and one Office doc, 8GB is fine. But heavy multitasking? Throw the extra RAM in.