PC Power Supply Calculator

Estimate system power draw, account for transient power spikes, and find the recommended power supply wattage for your PC build.

Unit: Watts
Unit: Watts
Unit: Watts
Recommended PSU: 1300W (Continuous Draw: 823W)
Nominal System Draw 823 W
Peak Estimate 1,273 W
Recommended PSU Capacity 1300 W
Nominal continuous power draw is 823 Watts. Transient excursions can peak at 1,273 Watts. To prevent sudden Over-Current Protection (OCP) shutdowns, choose a power supply of at least 1300W. Check your graphics card maker's recommended PSU rating as well.
Calculation: PSU = (450W × 2.0 transient) + 253W CPU + 120W misc = 1273W -> Rounded up to 1300W
Calculation basis: Continuous draw is GPU + CPU + other components. The peak estimate allows for brief GPU spikes of up to twice its rated power, then rounds up to the next 100 W.

How to Use This Calculator

  1. Enter the rated power of your graphics card and processor.
  2. Adjust the allowance for the motherboard, memory, drives and fans if needed.
  3. Compare the recommended rating with your graphics card maker's recommendation and use the higher of the two.

Frequently Asked Questions

Why does the calculator recommend more wattage than continuous system draw?

Modern high-performance graphics cards experience brief power spikes lasting milliseconds that can exceed rated continuous power. Sizing with headroom prevents shutdowns and trips.

What power supply standard suits modern high-power GPUs?

The ATX 3.0 and 3.1 specifications require power supplies to handle brief power excursions above their rating, which suits GPUs with short load spikes. Check the PSU's specification sheet for its ATX version.

Related Engineering Guides

Planning note: Results are planning estimates. Actual memory consumption, throughput, and power draw depend on inference runtime implementation (e.g. vLLM vs llama.cpp), batch size, and sequence context length. Benchmark your specific workload on physical hardware before purchasing.