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Choose a processor, graphics card, memory and cooling to see what the whole build costs, how much power it draws and which power supply it needs. Then scroll down and watch the case assemble in 3D.
Your parts
Parts only, at current US prices
Full breakdown
Your build, assembled
Drag to turn it · scroll to zoom · hit the power button on the case
How the power supply figure is worked out
Total draw, plus 40%, rounded up to the nearest 50W. That extra 40% covers two things: transient spikes, where a graphics card pulls far above its rated power for a few milliseconds, and headroom for a future upgrade so you are not replacing the unit twice.
It also puts most builds at roughly 55–70% load at peak, which is where a power supply is most efficient and where its fan spends the least time ramped up. A unit running at 95% of its rating works, but it runs hot and loud.
What each component actually draws
| Component | Under load | Notes |
|---|---|---|
| Graphics card | 75–450W | The single biggest figure, usually 55–65% of the total |
| Processor | 65–170W | Rarely at its limit while gaming |
| Motherboard | 35W | Broadly the same across boards |
| Memory | 5W per stick | Negligible either way |
| NVMe drive | 8W | Only under sustained writes |
| Hard drive | 9W | Spikes higher at spin-up |
| Case fan | 2W | A liquid cooler pump adds about 10W |
What the checks mean
Socket mismatch is the one that stops a build dead. A processor only fits the socket it was made for, and a board bought for the wrong one has to go back. This is the most common expensive mistake on a first build.
Lopsided pairing means one part is far ahead of the other. A fast graphics card behind a slow processor is held back at 1080p, though the gap mostly closes at 1440p and above. The warning is a prompt to check, not a reason to change your parts.
8GB of VRAM on a fast card matters at 1440p with high textures, where several recent releases stutter regardless of how quick the chip is. At 1080p it is still fine.
High transient spikes appear on cards rated above about 320W. Buy an ATX 3.x unit, which is built to handle those spikes to spec rather than by margin.
Questions about power supplies
Is a bigger power supply always safer?
No. A unit only delivers what the system asks for, so an oversized one is not dangerous — it is just money spent on capacity you never use, and it may run less efficiently at very low load.
Quality matters far more than wattage. A 650W unit from a well-reviewed platform is a better purchase than an 850W unit from a brand you have not heard of.
Can I reuse my old power supply?
If it is under about six years old, from a reputable line, and has the wattage and connectors you need, yes. Capacitors age, so a ten-year-old unit is worth replacing even if it still works.
This is the one component where being cautious is genuinely worth the money, because a failing unit can damage the parts attached to it.
What is the 12VHPWR connector and do I need it?
It is the newer single-cable connector on recent high-power graphics cards. Most cards ship with an adapter for standard 8-pin PCIe cables, so an older unit is not disqualified.
If you are buying new anyway, an ATX 3.x unit with a native cable removes the adapter and handles transient spikes properly. Not worth replacing a working unit for.
Does this account for overclocking?
Not directly. The figures are stock power limits. A meaningful processor overclock can add 30–60W, and raising a graphics card's power limit adds whatever you raise it by.
The 40% headroom absorbs a moderate overclock. If you plan to push hard, add the extra draw yourself and size up from there.
Where these numbers come from. Modelled from published benchmark data and manufacturer specifications — not measured on a bench here. Treat every figure as an estimate range, not a measurement. Prices are US street-price bands and move constantly; wattage is a calculated total with headroom, not a wall-socket reading. Dataset: 24 graphics cards, 16 processors, 31 games, reviewed October 2026. Full method →
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All reading the same hardware table, so the answers line up.