PSU Wattage Calculator
Estimate your PC's power draw from its components and get a recommended power-supply wattage with proper headroom. Sized for efficiency and GPU transients. Free.
The recommendation sizes the PSU so your system runs near ~55% load — where PSUs are most efficient and where there's headroom for boost-clock transients (modern GPUs spike well above their average) and battery-like capacitor aging. Buy an 80 Plus Bronze or better unit from a reputable maker; the efficiency rating and build quality matter more than chasing extra watts. GPU spikes are the main reason not to run a PSU near its limit.
Bigger isn't always better
The goal isn't the highest wattage — it's landing your typical load near 50–60% of the PSU's rating, where units are most efficient and quietest, with room left for spikes. A 450 W build doesn't benefit from a 1000 W unit; it just runs that unit inefficiently and costs more. What actually matters is an 80 Plus Bronze (or better) rating and a reputable manufacturer with a real warranty.
Why headroom matters
Modern GPUs draw far more than their average for milliseconds at a time (transient spikes), and a PSU's capacitors weaken as they age. Sizing with headroom absorbs both. If your build won't power on or reboots under GPU load with a marginal supply, the PSU is the first suspect — here's how to test a PSU with a multimeter or PSU tester.