What size power supply do you actually need?

Pick your CPU and GPU. We add the GPU’s board power and the CPU’s peak boost power (not its base TDP — an i9-14900K is a 125W chip that boosts to 253W), allow ~100W for the rest of the system, then pick the smallest standard size that still leaves at least ~25% reserve over that peak — room for GPU transient spikes and a future upgrade — and print the actual reserve the chosen size gives you. Every number is shown — no black box.

PSU wattage checker

Power figures are the manufacturers’ published numbers: GPU board power, and CPU peak boost power (Intel maximum turbo power / AMD PPT).

Why not just match the wattage exactly?

Because base TDP is not a ceiling. A modern CPU can draw double its base rating while boosting, and graphics cards draw short spikes well above their rated board power, a PSU runs most efficiently and quietly in the middle of its range, and a unit bought with headroom survives your next GPU upgrade instead of being replaced with it. Sizing to the exact watt is how systems end up shutting down mid-game.

What this checker does not know

Overclocking, large drive arrays, water-cooling pumps, and heavy USB loads all add draw. If any of those describe your build, step up one size from the recommendation. And wattage is only half the story: a quality unit from a reputable brand at the recommended size beats a cheap unit rated 200W higher.

Planning a GPU upgrade too? Run the pairing through the bottleneck calculator first so the new card is not held back by your CPU.