What power supply do I need?

Pick the part you already have. Every page carries the full table over the other side, sized on the processor's real power ceiling — not its TDP, which understates a Core i7-13700K by 128 W.

The number on the box is not the number that matters

Processors where the headline TDP most understates the power a supply must cover
Processor	Stated TDP	Real ceiling	Undercount
Core i7-13700K	125 W	253 W	+128 W
Core i9-13900K	125 W	253 W	+128 W
Core i7-14700K	125 W	253 W	+128 W
Core i9-14900K	125 W	253 W	+128 W
Core Ultra 7 265K	125 W	250 W	+125 W
Core Ultra 9 285K	125 W	250 W	+125 W
Ryzen 9 9950X	170 W	230 W	+60 W
Ryzen 9 9950X3D	170 W	230 W	+60 W
Ryzen 9 7900X	170 W	230 W	+60 W
Ryzen 9 7950X	170 W	230 W	+60 W

AMD publishes the ceiling as PPT — Package Power Tracking — at 1.35× the stated TDP. Intel publishes it as Maximum Turbo Power, and on the Core i9 parts it is twice the base figure. Every calculation here uses the ceiling.

By graphics card

AMD

Radeon RX 7900 XTX 355 W Radeon RX 7900 XT 315 W Radeon RX 9070 XT 304 W Radeon RX 7800 XT 263 W Radeon RX 7900 GRE 260 W Radeon RX 7700 XT 245 W Radeon RX 9070 220 W Radeon RX 7600 165 W Radeon RX 9060 XT 160 W

What the rest of the build costs

Power allowance for everything that is not the processor or the graphics card
Component	Each	Assumed	Notes
Motherboard	25 W	1	Chipset, VRM losses, onboard controllers. Enthusiast boards with extra controllers run higher.
Memory module	3 W	2	Per DIMM. DDR5 at high clocks sits at the top of this.
NVMe SSD	7 W	1	Per drive, at write load. Idle is under a watt.
SATA drive	8 W	0	Per drive. A spinning disk spikes higher on spin-up.
Case fan	2 W	3	Per fan. RGB models draw more for the lighting than the motor.
AIO pump	10 W	0	Per pump. Air coolers draw only their fan, already counted above.

44 W for the default build. Itemised rather than hidden in one lump, so a reader with four drives and nine fans can see why their number differs.

What decides the power supply a build needs

The figures below come from all 884 pairings of the 26 processors and 34 graphics cards here.

The processor's real ceiling

AMD's processors here draw up to 1.35× their stated TDP ; Intel's run from 1.27× to 2.02×. Sizing the supply from TDP instead picks a smaller unit than the build needs in 727 of the pairings (82%), by up to 200 W.

The card maker's recommendation

A graphics card's box names one supply size, and it has to assume some processor. Against the size computed for the whole build, the card maker's figure is larger in 517 pairings (58%), smaller in 158 (18%) and the same in 209. The recommendation takes whichever is larger.

Headroom

The computed size keeps the continuous load at or below 80% of the supply's rating. A Ryzen 7 7800X3D with a GeForce RTX 4070 draws 406 W continuously, which calls for 550 W; the card maker suggests 650 W, so the recommendation is 650 W and the supply runs at 62% of its rating.

Reading a processor or card page

Continuous load is itemised — the processor's ceiling, the card's board power and each platform part — so a build with more drives or fans can be adjusted line by line.
The page says which figure set the size: the build, the card maker, or both agreeing.
Wall draw depends on the efficiency rating. 406 W of components pulls about 478 W from the socket through an 80+ Bronze unit and 451 W through an 80+ Gold one.
Every part page carries the full table against every processor or card on the other side.

Common mistakes

Sizing from the TDP on the box. It comes up short in 82% of the pairings here.
Expecting a better efficiency rating to allow a smaller unit. It lowers the draw from the wall, not the load the supply has to carry.
Buying 1,000 W or more by default. Only 46 of the 884 pairings call for it.
Running at the edge. Transient spikes are not modelled, so a result within 50 W of a supply's rating is a reason to take the next size up.

Where to go next

Pick your card or processor above for the full table against the other part.
GPU running costs — what the same cards cost to run, by state.
Local LLM VRAM calculator — whether a card's memory holds a given AI model.
Methodology — the sizing formula, the platform allowances and the sources.

Frequently asked questions

How do I work out what PSU wattage I need?

Add the processor's power ceiling, the graphics card's rated board power and an allowance for the rest of the system — about 44 W for a typical build — then pick a supply large enough that the total sits at about 80% of its rating rather than at its limit.

Should I use my CPU’s TDP to size a power supply?

No. TDP is a thermal design target, not the socket's ceiling. A Core i7-13700K is sold as 125 W and draws 253 W when it boosts — 128 W more than its label. Use AMD's PPT or Intel's Maximum Turbo Power instead.

Why is the recommendation here sometimes higher than the graphics card maker’s?

A card maker publishes one figure per card, and it has to assume some processor. Pair the same card with a Core i9 instead of a Ryzen 5 and the system draws 165 W more, which is more than a whole supply size. Where the build needs less than the vendor's figure, the recommendation stays at theirs — they know how their own board handles transient spikes.

Does a bigger power supply use more electricity?

No. A supply draws what the components ask for, not what it is rated for. A larger unit running at half load is often slightly more efficient than a smaller one running near its limit, so the bigger unit can cost marginally less to run.

A sizing estimate, not a measurement. It adds the processor's power ceiling, the graphics card's rated board power and an itemised allowance for the rest of the system, then leaves headroom so the supply is not running at its limit. Real draw depends on the board's power profile, how far the parts are overclocked, and how a particular graphics card handles transient spikes. Treat a result within 50 W of a supply's rating as a reason to choose the next size up. Processor figures from AMD and Intel published processor specifications; card figures from Manufacturer specifications, shared with the GPU power dataset.

Data on this page last verified 11 September 2026. How these figures are calculated