PSU Wattage Calculator
List the power draw in watts of each part, and choose your headroom.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- Total = the sum of the parts you enter
- With headroom = total × (1 + headroom %)
- Recommended = that figure, rounded up to the next 50 W
To work out the electricity cost of running it, use the electricity bill calculator.
Worked example
CPU 125 W, graphics card 220 W, drives and board 50 W, fans 30 W, with 30% headroom:
- Total = 425 W, with headroom 552.5 W
- Recommended PSU = 600 W
Why your number may differ
Overclocking, extra drives and USB devices raise the draw. Always use a quality power supply with the connectors your parts need.
Frequently asked questions
How do I choose a power supply?
Add up the power use of the main parts, add some headroom, and choose the next standard size up from a reputable brand.
Why add headroom?
Power spikes, ageing and future upgrades. A power supply also runs most efficiently when the load is around 50% to 80% of its rating.
Where do I find each part’s power?
On the maker’s specification sheet, often called TDP, board power or maximum power. Graphics cards and CPUs use the most.