PSU Wattage Calculator
Pick your parts and get the recommended power supply size, with a transient-safe buffer built in.
Quick Summary · TL;DR
Recommended PSU = (CPU peak W + GPU peak W + ~80-120W system) × 1.25, rounded up to a standard size. For most single-GPU gaming builds in 2026 that lands between 550W and 850W. Always choose an 80+ Gold, ATX 3.0/3.1 unit.
How the calculation works
The estimator sums the realistic peak power of each component, then multiplies by 1.25. CPUs and GPUs dominate the total; storage, RAM, fans and peripherals add only a small fixed amount. The buffer matters because a power supply is happiest at 50-80% load and because modern graphics cards spike far above their average draw for milliseconds at a time.
| Component | Typical peak draw |
|---|---|
| Mid-range GPU | 150-260W |
| High-end GPU (RTX 5080/5090) | 360-575W |
| Gaming CPU | 76-253W |
| Board + RAM + drives + fans | ~80-120W |
Frequently asked questions
What size PSU do I need for my PC?
Add up the CPU and GPU peak power, plus about 80-120W for the rest of the system, then add a 25% buffer. This calculator does that for you and rounds up to the nearest standard PSU size.
Why add a 25% buffer instead of buying the exact wattage?
Modern GPUs produce millisecond transient spikes that can briefly double their rated draw, and PSUs are most efficient at 50-80% load. A 25% buffer covers both and extends the unit's lifespan.
Do I need an ATX 3.0 or 3.1 power supply?
If you run a modern NVIDIA RTX 40/50-series card, yes; ATX 3.x units include the native 12VHPWR connector and are rated to ride out transient spikes without shutting down.
Building from scratch? Start with a balanced parts list using the Auto PC Builder, or check pairing with the Bottleneck Estimator.