By Tim King · Updated 7 October 2026

PSU Calculator

PC and GPU Power Supply Wattage Needed

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Processor

Graphics card

Memory sticks

SSDs

Hard drives

Case fans

AIO liquid cooler

Overclocking

Result

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How the PSU Wattage Calculator works

This PSU calculator works out the PC wattage your build draws and the power supply size to buy. Choose your processor and graphics card, enter how many memory sticks, drives and fans the build has, and say whether it uses a liquid cooler or anything is overclocked. It adds up the realistic gaming load and the momentary spikes the GPU can pull on top, then recommends a standard PSU wattage that keeps the sustained load in the efficient middle of the unit's range.

A PSU calculator that sizes for spikes, not just watts

A power supply that is too small shuts the PC off when the graphics card spikes; one that is too big wastes money. This PSU calculator keeps gaming draw under 70% of the label with the worst-case spike still inside it.

The formula

Gaming load = CPU heavy-load power × 0.65 + GPU board power + the rest of the system. The rest is a 40 W base for the motherboard and USB, plus 4 W per memory stick, 6 W per SSD, 9 W per hard drive, 3 W per fan and 20 W for an AIO pump. Transient peak = gaming load + half the GPU's board power. Recommended PSU = the smallest standard size at or above both the peak and the load ÷ 0.7. A mild overclock multiplies CPU and GPU power by 1.1, and a heavy one by 1.25.

CPU figures are measured all-core package power, not box TDP: a Ryzen 7 7800X3D rarely passes 95 W, an i9-14900K reaches 260 W. Games load cores unevenly, hence the 0.65.

Why transient spikes decide the size

For a millisecond or two, a modern GPU can draw half its rating again or more. The average load does not trip an undersized unit's over-current protection; these excursions do. Intel's ATX 3.0 and 3.1 specifications answered this. They require a supply to tolerate excursions of up to twice its rating for 100 microseconds. They also brought the 12VHPWR connector, revised as 12V-2x6. That is why high-end cards get an ATX 3.x recommendation here.

Worked examples

The first example is a mid-range build: a Ryzen 5 7600, an RTX 4060, two sticks, one SSD and three fans. The gaming load is about 250 W, with a peak of 307 W. Both 450 W rules are met, so the recommendation and the minimum are 450 W.

The second example is a flagship build: an i9-14900K and an RTX 4090 with two SSDs, five fans and an AIO. The load is 714 W and the peak 939 W. At 714 ÷ 0.7 = 1,020 W, 1000 W falls just short, so the answer is 1200 W.

GPU PSU wattage: how many watts each graphics card needs

Every build below uses a Ryzen 7 7800X3D, two memory sticks, one SSD, three fans and no overclock.

Recommended PSU by graphics card, 7800X3D build

Graphics card	Gaming load	Transient peak	Recommended PSU
GTX 1660 Super	250 W	312 W	450 W
RTX 2060	285 W	365 W	450 W
RTX 3060 12GB	295 W	380 W	450 W
RTX 3070	345 W	455 W	550 W
RTX 3080	445 W	605 W	650 W
RTX 4060	240 W	297 W	450 W
RTX 4060 Ti	285 W	365 W	450 W
RTX 4070	325 W	425 W	550 W
RTX 4070 Super	345 W	455 W	550 W
RTX 4080 Super	445 W	605 W	650 W
RTX 4090	575 W	800 W	850 W
RTX 5060	270 W	342 W	450 W
RTX 5070	375 W	500 W	550 W
RTX 5070 Ti	425 W	575 W	650 W
RTX 5080	485 W	665 W	750 W
RTX 5090	700 W	987 W	1000 W
RX 6800 XT	425 W	575 W	650 W
RX 7600	290 W	372 W	450 W
RX 7800 XT	388 W	519 W	650 W
RX 7900 XT	440 W	597 W	650 W
RX 7900 XTX	480 W	657 W	750 W
RX 9060 XT	285 W	365 W	450 W
RX 9070	345 W	455 W	550 W
RX 9070 XT	429 W	581 W	650 W
Intel Arc B580	315 W	410 W	450 W

How to read the result

Estimated gaming load is the sustained draw, split into CPU, GPU and the rest.
Transient peak the PSU must ride out is the load plus spike allowance. The label must cover it.
Recommended PSU and Why that size give the standard size that keeps the load under 70%.
Minimum you could get away with is the load at 85% of a quality ATX 3.x unit. It works today, but leaves nothing for a GPU upgrade.
Suggested efficiency tier rises to Gold for loads over 400 W. For cards of 300 W and up, it adds ATX 3.x with a native 12V-2x6 connector.

The table under the result shows this build on every size from 450 to 1600 W, marked Too small, Marginal, Works, Good or Oversized.

Tips and pitfalls

Quality beats wattage. A cheap 750 W unit with weak protection is worse than a good 650 W one. Long warranties signal confidence.
Efficiency ratings describe the bill, not the capacity. A Gold unit delivering 500 W draws about 555 W from the wall, and a Bronze one about 600 W. Cost it with the electricity cost calculator.
Undervolt before upsizing. Many recent GPUs lose 50–100 W with no frame-rate loss.
Check balance, not just power. The bottleneck calculator shows whether the CPU and GPU are matched before you size for them.

Sources: Thermal design power.

Checked against: Recommended PSU = estimated load plus headroom, rounded up to a stock wattage

FAQ

Is a 650 W PSU enough for an RTX 4070?

Yes, comfortably. An RTX 4070 with a mid-range processor draws about 320 W in games and spikes to around 420 W. A quality 550 W unit handles that at 58% sustained; Nvidia's official 650 W figure is right in the ideal range and leaves room for a bigger card later.

What PSU do I need for an RTX 5090?

At least 1000 W, and 1200 W is sensible with a high-end processor or any overclocking. The card's 575 W rating spikes toward 1000 W briefly, so an ATX 3.1 unit with a native 12V-2x6 cable is strongly recommended rather than an adapter.

Does a bigger PSU use more electricity?

Not meaningfully. A supply only draws what the components ask for, plus its conversion loss. An oversized unit runs at a lower percentage load, which slightly reduces efficiency below 20% load but is otherwise harmless. Buy for headroom, not for the smallest label that works.

What happens if my PSU is too weak?

Under sustained overload it runs hot, its fan screams and it ages fast. Under a transient spike, its protection trips and the PC shuts off instantly, often mid-game. Cheap units without good protection can fail and take other components with them.

Should I get 80 Plus Gold or Bronze?

Gold if the budget allows. The efficiency difference is small in money terms, but Gold units are generally built to a higher standard with better capacitors, quieter fans and longer warranties, and are more likely to meet ATX 3.x for modern graphics cards.