PSU wattage calculator
Find your GPU and CPU wattage on their spec pages, put them in, and get the supply size worth buying — headroom already accounted for.
Why headroom isn't optional
Your components' rated figures are sustained draw, but modern GPUs pull brief spikes far above their rating — sometimes close to double, for milliseconds. A supply sized exactly to your rated total will trip its protection during those spikes and shut the machine off mid-game, which looks exactly like a failing GPU and sends people down the wrong diagnostic path for weeks.
The 35% margin above covers spikes, capacitor ageing over the years, and the fact that supplies run most efficiently around half load rather than flat out. It also leaves room for the upgrade you'll make in two years, which is nearly always a hungrier GPU.
Two things matter more than extra watts once you're sized correctly. Efficiency rating (80+ Bronze through Titanium) affects heat, noise and your power bill, not stability. Connector type matters more than either — recent high-end cards need a 12V-2x6 connector, and using an adapter with a supply that lacks one is where the melted-connector stories come from. Check the connector before you check the wattage.
Don't over-buy either: a 1200W unit running a 350W system sits in its least efficient range and costs more for nothing.
Questions
Where do I find my GPU's wattage?
Manufacturers list it as TGP, TBP, or 'total graphics power' on the product page. Use the board partner's figure for your exact card, not the reference number — factory-overclocked cards genuinely pull more.
Is a bigger PSU always safer?
Up to a point. Headroom is good, but a hugely oversized unit runs in its least efficient load range and costs more up front. Roughly 1.3–1.5× your real peak draw is the sweet spot.
Does the 80+ rating affect what size I need?
No — efficiency describes how much wall power gets wasted as heat, not how much your components draw. It affects your electricity bill, temperature and fan noise, not the wattage you need to buy.
My PC shuts off under load. Is it the PSU?
It's a common cause, especially with a supply sized too close to your peak draw or one that's several years old. But overheating and driver faults produce the same symptom — check temperatures before buying anything.