PSU Calculator
Choose your graphics card and processor; the rated power of each comes from our hardware table. Add the rest of the build and you get a supply size with room for the power spikes that trip undersized units.
Pick your parts and press the button.
The rule behind the number
- Rated power of the graphics card and processor.
- + 60 W for motherboard, memory, the boot drive and USB devices; + 3 W per fan and + 8 W per extra drive.
- × 1.4 for spikes and ageing.
- Round up to the next common size: 450 W, 550 W, 650 W, 750 W, 850 W, 1000 W, 1200 W, 1300 W, 1600 W.
The hungriest desktop card we track is the NVIDIA GeForce RTX 5090 at 575 W on its own.
Power supply questions
Why add so much headroom?
Graphics cards draw brief spikes well above their rated power when a scene changes suddenly. A supply sized to the average can trip its protection and switch the PC off, so the calculator leaves 40% on top.
Is a bigger power supply wasteful?
Not in any way you would notice. A supply only delivers what the PC asks for; a larger one simply runs cooler and quieter at the same load.
Where do the wattages come from?
Each graphics card and processor carries its rated power (TDP or board power) from our hardware table. Processors can briefly exceed their rating, which the headroom also covers.
Which efficiency rating should I pick?
80 Plus Gold is the usual choice for gaming PCs. The rating changes how much power is wasted as heat, not how much the PC can draw.