PSU Wattage Calculator

A power supply sizing tool for a PC build. You enter what each part draws at full load, along with the headroom you want and the efficiency rating of the unit, and it returns the total load, the next supply size commonly sold above it, where that leaves the unit on the efficiency curve and how much the machine pulls from the wall. A second mode checks a supply you already own against a load. There is no built-in parts list: every wattage is one you supply from the manufacturer's own specification page, so the tool does not go stale when a new card ships.

Calculator Type

Enter what each part draws at full load, from its specification page. Leave a line at zero if the build has none of it.

The maximum turbo power or PPT from the manufacturer, which is usually well above the advertised TDP.
Zero for integrated graphics. Add the cards together if there is more than one.
A spinning hard disk draws more than an SSD, and more again while it spins up.
Capture cards, fan controllers, USB devices drawing from the board, water cooling accessories.
Room for spikes, for a part you add later, and for the way a unit ages. Twenty to thirty per cent is the usual choice; more if you plan to overclock.
A measured or reviewed figure for your own unit at the load it will actually run at. It overrides the rating when filled in.
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For a unit you already own or already bought: how much room is left above the load, and where that puts it on the efficiency curve.

The continuous rating on the label, not a peak figure.
Add your parts up on the other tab first if you do not have this figure.
A measured or reviewed figure for your own unit at the load it will actually run at. It overrides the rating when filled in.
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