How to calculate the number of watts for every addiotnal part to my pc?

Question

Could you help me how to calculate the number of devices I could add to my computer safely to the limit of the power supply (290 watt)

I have Dell 9020 core i5 tower pc

and I want to add the following:

• Internal SATA black western harddisk 3tb
• Internal SATA harddisk 1tb samsung

in addition to the existing 500 gb blue western harddisk

• 1 RAM DDR3 -->4gb in addition to the existing one so the sum = 8 gb
• 2tb external usb harddisk

Is this safe?

Answer 1

I think it's safe to add these components. To be sure, use a wattage calculator like this:

https://outervision.com/power-supply-calculator