Power Supply Calculator
Calculate PSU wattage needed
🔒 No tracking · Method · · Disclaimer · Power Supply Calculator
Power Supply Calculator is built for calculating PSU wattage needed — fast, free, and private. Drop CPU TDP (watts), GPU TDP (watts) and RAM Sticks into Power Supply — the figure refreshes as you type. Power Supply displays each intermediate figure as well. Power Supply replaces guesswork. No account is needed for Power Supply. The browser does the arithmetic. Power Supply sits in the Tech & Digital section next to free online power supply calculator and power supply wattage. Power Supply shows formula, assumptions and result together. Power Supply answers the next Tech & Digital question you meet.
What the defaults give
The build draws about 598 W, and the recommended supply is 750 W.
The recommendation adds 25% headroom to the estimated draw, which covers transient spikes from the graphics card and leaves the supply running near its efficient range.
How the estimate is built
Draw = CPU TDP + GPU TDP + (RAM sticks × 7 W) + (drives × 15 W) + 50 W platform
125 + 350 + 28 + 45 + 50 = 598 W. The supply recommendation is 598 × 1.25 = 747.5, rounded up to the next 50 W step: 750 W.
Worked examples
125 W CPU, 350 W GPU, 4 RAM, 3 drives → 598 W, 750 W supply
65 W CPU, 150 W GPU, 2 RAM, 1 drive → 294 W, 400 W supply
180 W CPU, 450 W GPU, 4 RAM, 4 drives → 748 W, 950 W supply
35 W CPU, no GPU, 2 RAM, 1 drive → 114 W, 150 W supply
Why headroom, not a bigger number
A supply runs most efficiently around 40–60% of its rating, and modern graphics cards draw brief spikes well above their stated TDP. Sizing at exactly the estimated draw leaves no room for either. Sizing 25% above it usually keeps the average load in the efficient band and absorbs the spikes without triggering a shutdown.
What TDP does not tell you
- Peak versus sustained. A card rated at 350 W can pull 450 W for milliseconds during a load transition.
- Overclocking. Manual tuning can add 20% or more to both CPU and GPU draw.
- Peripherals. Fans, RGB, pumps and USB devices each take a few watts that add up.
- Efficiency and heat. A cheaper supply rated at 750 W may deliver far less comfortably at high load, and its efficiency rating matters more than its sticker.
Check the 12V rail rating rather than the total wattage, since that is what the CPU and GPU actually use.
Frequently Asked Questions
What PSU do I need for a 350 W GPU?
About 750 W with a 125 W CPU, four RAM sticks and three drives, because the estimate comes to 598 W and a 25% margin pushes it to 750.
Why add 25% headroom?
For transient spikes and efficiency. Supplies run best around half load, and a card rated at 350 W can peak well above it.
Is a bigger PSU always better?
No. A hugely oversized supply runs inefficiently at low load and costs more. Size to the build with a modest margin.
Does RAM really use 7 watts a stick?
As a planning figure, yes — 3–10 W per stick is typical. The exact number matters less than the GPU and CPU lines.
What about the 12V rail?
It carries almost all the CPU and GPU load, so check that its rating covers those two components rather than trusting the total wattage.
Does overclocking change the recommendation?
It can add 20% or more to the draw. Recalculate with higher TDP figures if you plan to tune the CPU or GPU.
RAID Usable Capacity Calculator and other Tech & Digital tools
RAID Usable Capacity Calculator · Bandwidth Calculator · SSD vs HDD Speed · Image File Size Estimator · Cloud Data Transfer Cost · Text Case Converter · Tech & Digital Guides