How the wattage is estimated
- The graphics card counts at its full board power (TGP or TBP), the figure its maker publishes. It is the largest single load in a gaming PC.
- The processor counts at a typical gaming load: games rarely keep every core at the turbo limit. Turn on Overclock / unlocked power limits and it counts at its maximum turbo power (Intel) or PPT (AMD) instead, which is what long renders and lifted BIOS limits reach.
- The motherboard, memory, drives, fans, cooler pump, RGB strips and USB devices each add a small fixed amount. The breakdown under the result lists every part, so you can see where the watts go.
- Part not in the list? Choose Not listed: enter watts and type the power from its spec page.
Why the result is bigger than the load
A power supply should not run flat out. The calculator adds headroom so the estimated load sits near 60% of the PSU's rating. That keeps the PSU close to half load, where 80 Plus units waste the least power and their fan stays quiet, and it leaves margin for power spikes, ageing capacitors and a future upgrade. The result is then rounded up to a size you can actually buy.
When the graphics card maker publishes a recommended system power and it is higher than the estimate, the calculator uses the maker's figure. That recommendation assumes a high-end processor, so it can look generous next to a modest build.
Graphics card power spikes
Modern graphics cards draw short spikes, lasting milliseconds, well above their rated board power. Older power supplies can read those spikes as an overload and switch off, which looks like a random restart in the middle of a game. The calculator models the spikes as one and a half times the card's board power on top of the rest of the load, and never suggests a PSU smaller than that peak.
If your PC shuts off or restarts under load while temperatures look fine, a PSU that cannot handle GPU spikes is a common cause. Check the PSU's age and whether it meets ATX 3.0 or 3.1.
80 Plus vs ATX 3.1
- 80 Plus (White, Bronze, Silver, Gold, Platinum, Titanium) rates efficiency: how much of the power drawn from the wall reaches your parts instead of turning into heat. Gold or better is a good target for a gaming PC.
- ATX 3.0 and 3.1 are design standards from Intel. They require the PSU to ride out short power spikes well above its rating, and they add the 12V-2x6 cable for recent graphics cards. ATX 3.1 updates the connector to 12V-2x6, which seats more reliably than the earlier 12VHPWR.
- The two labels answer different questions. An ATX 3.1 PSU can be Bronze or Platinum; an 80 Plus Gold unit can be an old ATX 2 design. For a recent graphics card, look for both.
Power connectors
- Processor: every desktop board needs an 8-pin EPS (CPU) cable. Boards for high-power processors often have a second 4+4 or 8-pin socket; connect it when the PSU has the cable.
- Graphics card: older and mid-range cards use 6-pin or 8-pin PCIe cables. Recent NVIDIA cards use one 12V-2x6 (12VHPWR) cable, rated for a set wattage; the card's adapter can take several 8-pin cables instead.
- Use a separate PCIe cable for each socket on the card when the PSU has enough, instead of both ends of one daisy-chained cable.
- Push the 12V-2x6 plug in until it clicks and sits flush, and do not bend the cable sharply right at the plug.
- The calculator lists the reference card's connectors. Some card makers use different ones, so check your card's box or spec page.
Before you buy
Treat the result as an estimate from the vendors' published specs. Read your graphics card maker's PSU guidance, buy from a brand with a long warranty and good reviews, and check that the PSU has every cable in the list. A larger PSU costs a little more but does no harm: the PC only draws what it needs.
Questions
How many watts does my PC need?
Add the graphics card's board power, the processor's power and a small amount for every other part, then add headroom. The calculator does this for your parts and rounds up to a common PSU size.
Is a bigger power supply bad for my PC?
No. A PC draws only the power its parts use. A larger PSU costs more and can be slightly less efficient at very low loads, but it does not harm your parts.
Why does the calculator suggest more than the estimated load?
It adds headroom so the load sits near 60% of the PSU, covers graphics card power spikes, and never goes below the card maker's recommendation.
Do I need an ATX 3.1 power supply?
For cards with a 12V-2x6 connector, an ATX 3.1 PSU with a native cable is the cleanest choice. For other cards it is optional but helps with power spikes.
What does 80 Plus Gold mean?
It is an efficiency rating: at typical loads, most of the power taken from the wall reaches your parts. It says nothing about the connectors or how the PSU handles spikes.
My graphics card is not in the list. What do I do?
Choose Not listed: enter watts and type the board power (TGP or TBP) from the card's spec page or box. Then check its power connectors on the same page.