How the estimate works
The two parts that matter most are the processor and the graphics card. Together they usually make up 80% or more of a gaming PC's power draw. This calculator uses each CPU's maximum package power (what it can sustain under heavy load) and each graphics card's official total board power, then adds typical figures for everything else.
It then recommends a power supply rated so your peak load sits around 70% of its capacity. That leaves headroom for brief GPU spikes, keeps the PSU in its efficient range and lets you upgrade later.
The formula
recommended PSU = load ÷ 0.7, rounded up to a standard size
Example: Ryzen 7 9800X3D + RTX 4070
| Part | Watts |
|---|---|
| CPU (max package power) | 162 |
| GPU (total board power) | 200 |
| Motherboard, USB, 2 RAM sticks, 1 SSD, 4 fans, pump | 109 |
| Estimated peak load | 471 |
| 471 ÷ 0.7 = 673 → next size up | 750 W |
Buying tips
- Quality over watts. A good 750 W unit from a reputable maker beats a no-name 1000 W one. Look at independent reviews.
- ATX 3.x for new GPUs. Current high-end NVIDIA cards use the 12V-2x6 connector; a native cable avoids bulky adapters.
- Gaming draw is lower than peak. Games rarely max the CPU and GPU at the same moment, so typical draw is often well under the peak shown.
Frequently asked questions
How many watts does my gaming PC need?
Add the CPU's maximum package power and the graphics card's total board power, then about 75 to 100 watts for the motherboard, memory, drives, fans and USB devices. Buy a power supply rated about 40% above that total so it runs efficiently and handles brief spikes.
Is a bigger power supply bad?
No. A PC only draws the power it needs, so an 850 W unit in a 400 W system is fine. Oversized units cost more and can be slightly less efficient at very low loads, but they run cooler and quieter and leave room for upgrades.
What are GPU power spikes?
Modern graphics cards can briefly pull well above their rated power for a few milliseconds. Cheap or undersized power supplies can shut off when that happens. ATX 3.0 and 3.1 power supplies are designed to handle these spikes, which is why they're recommended for current high-end cards.
Should I trust the GPU maker's recommended PSU?
It's a safe starting point. NVIDIA and AMD list a recommended system power for each card, set high to cover any CPU paired with it. This calculator gives a figure for your specific parts, which is often a little lower; when the two differ, go with the larger one.
What efficiency rating should I get?
80 Plus Gold is the sweet spot for most gaming PCs. Efficiency affects your electricity bill and heat, not how many watts the PSU can deliver: a 750 W Bronze and a 750 W Gold unit both supply 750 W to your parts.
Rates and figures last checked October 2026.
This calculator gives estimates for planning. Check current rates and product labels before you buy, list or file.