It's hard to say, because I also need to know what kind of case fans, motherboard, storage, and if you have any sound cards, as these can heavily impact what power supply you need. A good website to see how much power your PC is going to need is PCPartPicker.com
If you click on the "view my system build" button, you can choose all of the parts that you will be using, and then it will tell you how many watts you're going to need. A good rule of thumb is to always get a power supply 25% stronger than the wattage of your computer. For example, if you have a 750 watt PC, you should probably get a 1000 watt PSU.