Power Optimization

Power supply calculator.

Total Nominal Power

50w

Total Nominal Power

50w

Suggested PSU

650 W

Find on Amazon

Where the watts go

Board, RAM, SSD

50 W

Load on common supply sizes

650 W8%750 W7%850 W6%1000 W5%1200 W4%1600 W3%

Green is the comfortable band (35–70 %), amber leaves little margin for spikes, red is too small. Each size opens a search for it.

Based on real consumption data and theoretical peaks.

Series

How the power supply recommendation is worked out

The calculator adds up what your parts draw, leaves a margin on top and rounds to a size you can actually buy. Here is each step, five real builds run through it, and the cases where you should buy a size up.

Using it

Choose the processor and the graphics card. Between them they account for most of what a gaming PC draws, so these two decide the answer.
Add the extras if you have them: the cooler's pump and fans, case fans, lighting and other devices. Each adds a few watts; together they can move a build across a 100 W step.
Read the breakdown under the total. It shows where the watts go, which usually settles the question of whether the RGB matters (it rarely does).

The three steps behind the number

System draw = graphics card rated power + processor rated power + 50 W for the motherboard, memory and a drive, plus anything you added.
Headroom: the draw is multiplied by 1.25. Graphics cards draw brief spikes well above their rating, and a supply that sits at its limit runs hotter, louder and less efficiently.
Rounding: the result goes up to the next 100 W, because that is how supplies are sold, and never below 650 W, because good units below that are hard to find and cost about the same.

Five builds, worked through

Ryzen 5 7600 + RTX 5060 Ti: 65 + 180 + 50 = 295 W. With headroom that is 369 W, which rounds to 400 W — but the floor lifts it to 650 W. A quality 650 W unit is the sensible minimum, and it leaves room for a bigger card later.
Ryzen 7 9800X3D + RTX 5070 Ti: 120 + 300 + 50 = 470 W, × 1.25 = 588 W, rounded to 600 W and lifted to 650 W. At 300 W this card uses the 12V-2x6 connector, so a supply with a native cable is worth choosing.
Ryzen 7 9800X3D + RTX 5080: 120 + 360 + 50 = 530 W, × 1.25 = 663 W, rounded up to 700 W.
Core i7-14700K + RTX 4090: 253 + 450 + 50 = 753 W, × 1.25 = 941 W, rounded up to 1,000 W. The 253 W is the processor's turbo limit, not its base figure, so this one is already sized for a processor running flat out.
Ryzen 9 9950X + RTX 5090: 170 + 575 + 50 = 795 W, × 1.25 = 994 W, rounded up to 1,000 W. It lands just under the step; with a large liquid cooler and many fans added, it crosses into 1,100 W territory, and a 1,200 W unit is the comfortable choice.

When to buy one size up

Rated power is not peak power. AMD processors are allowed to draw about 1.35 times their rated figure by default, so a 120 W Ryzen 7 9800X3D can pull around 160 W under a heavy all-core load. Overclocking, raising power limits in the BIOS, or a graphics card with a factory overclock all add to the real draw. If any of that applies, go one step above the recommendation.

Buying bigger does not cost you electricity: a supply delivers what the parts ask for, not its label. What a bigger unit costs is money up front, so the margin is worth paying for when you plan to upgrade the graphics card within the life of the supply, which is often ten years.

Wattage is only half of it

Two 750 W supplies can be very different products. Look for a recent ATX 3.1 unit if your card uses the 12V-2x6 connector, an 80 PLUS Gold rating or better, and a long warranty, which is the clearest sign of what the maker expects from its own parts. The figures used for every part, and the limits of the method, are on the methodology page. To see what the finished build costs to run, take its draw to the electricity cost calculator.

Frequently asked questions

How many watts does my PC really need?

Add the processor's TDP and the graphics card's board power — together they are typically 80% of the total — then allow roughly 50 to 80 W for the board, drives, memory and fans. The calculator does this for you from the parts you select.

Why leave 25% headroom instead of buying exactly what I need?

Three reasons. Modern graphics cards draw brief spikes well above their rated power, and a supply running at its limit can shut down on one. Efficiency peaks near half load, so a unit that is always maxed out runs hotter and louder. And capacitors age: a supply delivers a little less after a few years than it did new.

Does a larger power supply waste electricity?

No. A power supply draws what the components ask for, not what it is rated for. A 1000 W unit powering a 400 W machine consumes the same at the wall as a 600 W unit doing the same job — slightly less, in fact, because 40% load sits closer to its efficiency peak.

Do I need an ATX 3.1 supply with a 12V-2x6 connector?

Only if your graphics card uses that connector. Cards that do will run from an adapter off an older supply, but a native cable is tidier and avoids the adapter becoming the weak point. Everything else works fine on a good ATX 2.x unit.

Is 80+ Gold worth paying for over Bronze?

The efficiency difference is a few percent, so it rarely pays for itself in electricity alone. What you are usually buying with the higher rating is better components, a quieter fan curve and a longer warranty — which matters more, because the power supply is the one part that can take others with it when it fails.

Keep going

Other tools and reference pages that pick up where this one leaves off.

Assembly simulator Build a PC piece by piece and check it boots. Build configurator Complete, coherent parts lists by budget. Bottleneck detector See whether the CPU or the GPU is holding you back. LLM VRAM calculator Check whether a model fits on your card. Air vs liquid cooling Which one your build actually wants. Hardware glossary Every term on this site, explained plainly.

Run a site about PC hardware? Put this calculator on it