PC Power-Supply Estimator
Loading this tool…
If the tool does not appear, check your connection and reload this page.
Enable JavaScript to use the estimator. The calculation method and example below remain available.
Understand your power-supply estimate
Choose realistic component-load inputs
Enter CPU package power and total graphics-card power for the workload you want to plan around, then allow for the motherboard, memory, drives, fans, and other devices. Use relevant measurements or manufacturer specifications and label your assumptions. Do not enter the PSU's advertised capacity as a component load. The default numbers are an example, not a detected PC configuration.
How headroom and transient allowance are combined
Sustained load is CPU + GPU + other load. The transient envelope is CPU + other load + GPU × the selected factor. The headroom target is sustained load × (1 + headroom percentage ÷ 100). This tool takes the larger of those two targets and rounds up to the next 50 W increment. It does not add the two allowances together; the GPU multiplier is a planning scenario, not a measured power excursion or ATX compliance test.
Worked example: 570 W sustained load
The default 150 W CPU, 320 W GPU, and 100 W other load total 570 W. With a 1.30× GPU factor and 25% headroom, the transient envelope is 666 W and the headroom target is 712.5 W. The larger target rounds up to 750 W. Sustained utilization is 76.0%, and estimated wall draw at 90% efficiency is 633.3 W.
PSU capacity is not wall consumption
The rated wattage describes output capacity, not constant wall draw. Estimated wall power here is sustained component load divided by the assumed efficiency fraction. Changing efficiency affects that estimate, not the required DC output capacity. Actual efficiency varies with operating conditions; this single assumption does not predict idle power, noise, or electricity costs.
Verify connectors and the exact PSU model
The connector selector only displays a planning note. Verify the graphics-card requirements, PSU specifications, cable compatibility, physical fit, and installation instructions for the exact hardware. Use only cables explicitly approved for that PSU model; connector appearance alone is not proof of compatibility. The rounded wattage does not certify quality, protections, transient response, or safe compatibility, and available retail capacity tiers may differ.