Building your own PC, rather than buying one off the shelf, can be very rewarding. And it can save you money too. But there are lots of important things you need to consider, such as making sure that the CPU, motherboard and RAM are all going to fit together.
But before all that, you need to buy a case and a power supply. And it can be difficult to know how big a PSU you're going to need.
So here's a great way of finding out. Just use the free PSU Calculator at http://educations.newegg.com/tool/psucalc/index.html. Tell it the type of CPU you're using, and how much RAM, and what sort of processor, etc etc, and it'll give you a pretty good estimate of the number of watts your PSU needs to be capable of putting out. It'll also link you to some suitable power supplies that the site happens to sell, of course, but you can always shop elsewhere if you'd rather.
This is a pretty specialised area, but such an online tool is definitely handy. Whether you're planning to build a new machine from scratch, or whether you're planning a big hardware upgrade and you need to know whether the existing PSU will be up to the job.
My thanks to reader "Gator" for this hot find.