Power Supply Calculator
Enter your system's base power load and a headroom percentage to find the recommended power supply wattage.
Headroom provides a safety margin above your typical load for peak demand and efficiency.
How recommended power supply wattage is calculated
This calculator adds a headroom percentage on top of your system's base power load: recommended wattage = base load × (1 + headroom%). This margin accounts for brief power spikes above typical load, and keeps the power supply operating in its efficient range rather than near its maximum capacity.
A common recommendation is 20-30% headroom above typical load for most electronics and computer systems, since power supplies are generally most efficient and have the longest lifespan when running at 50-80% of their rated capacity rather than near 100%.
Frequently asked questions
Why not just buy a power supply that exactly matches my load?
Running a power supply near its maximum rated capacity reduces efficiency, generates more heat, and shortens its lifespan. It also leaves no margin for momentary power spikes or future component upgrades that increase total load.
How do I find my system's base power load?
For a PC build, add up the rated power consumption (TDP or max power draw) of each major component — CPU, GPU, motherboard, storage, fans, and so on — or use a dedicated PSU calculator tool specific to your component list for a more detailed estimate.
Is more headroom always better?
Not necessarily — an oversized power supply running at very low load percentages can actually be less efficient than one properly sized with modest headroom, since most power supplies have a specific load range where efficiency peaks.