Can I run a 300 W card on a 500 W PSU?

Only if the CPU and the rest of the system are very frugal — the calculator adds them up, and transient spikes can still shut the machine down.

Why is the result rounded to 50 W steps?

Power supplies are sold in those steps, so the calculator recommends the next size you can actually buy.

Power & PSU calculators

Add the graphics card, processor and the rest of the system to size the power supply correctly.

W = (GPU + CPU + rest) × (1 + margin/100), rounded up to the next 50 W step

Modern graphics cards draw short transient spikes well above their rated TDP, so a 20–30 % margin keeps the protection circuit from tripping.
Efficiency matters too: a PSU is most efficient at roughly 50 % load, which is another reason not to buy oversized units.

Graphics card TDP(W)

Processor TDP(W)

Rest of the system(W)

Safety margin(%)

550 W

≈ 520 W

Formula: W = (GPU + CPU + rest) × (1 + margin/100), rounded up to the next 50 W step
Example: GPU TDP: 200 W CPU TDP: 125 W Rest of system: 75 W Safety margin: 30 % Raw need: 520.0 W Recommended PSU: 550 W

Example

GPU TDP: 200 W
CPU TDP: 125 W
Rest of system: 75 W
Safety margin: 30 %
Raw need: 520.0 W
Recommended PSU: 550 W

Can I run a 300 W card on a 500 W PSU?: Only if the CPU and the rest of the system are very frugal — the calculator adds them up, and transient spikes can still shut the machine down.
Why is the result rounded to 50 W steps?: Power supplies are sold in those steps, so the calculator recommends the next size you can actually buy.

Copies: 7,310 · Views: 18,450 · Updated: Sep 18, 2026

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