How the calculator works
The estimate adds GPU board power, CPU package power and allowances for the motherboard, RAM, storage, fans, cooling and USB devices. It then adds operating headroom and extra transient allowance for high-power GPUs.
Power Supply Calculator
Estimate maximum system load and choose a sensible PSU with transient and upgrade headroom.
Live catalog dataNo fake precisionShareable result
H2HBench
Select the required hardware to calculate a result.
- Live catalog data
- No fake precision
- Shareable result
- confidence
How to interpret the result
Minimum is the nearest standard capacity above calculated peak demand. Recommended wattage keeps the PSU away from continuous maximum load, and upgrade headroom leaves space for a future component.
Factors that affect the result
Actual wall power depends on PSU efficiency, component power limits, transient behavior, overclocking and workload. Choose a quality unit with the connectors required by your hardware.
Frequently asked questions
How much PSU headroom should I use?
A 25–35% margin is practical for most systems, with more transient allowance for high-end graphics cards.
Is a higher wattage PSU dangerous?
No. The PC draws only the power it needs, but build quality and protections matter more than an oversized label.
Does efficiency rating change wattage?
Efficiency mainly changes wall consumption and heat. Capacity should still cover component output demand and transient peaks.