The PC power supply calculator estimates total wattage for your build and recommends the minimum PSU size with proper headroom. Accurate sizing prevents power shortages and ensures long PSU lifespan.
Calculate PSU Wattage
Check CPU specs page (e.g. i5: 65W, i9: 125-150W)
Check GPU specs (e.g. RTX 3070: 220W, 4090: 450W)
How to Choose the Right Power Supply
Power supply sizing depends on your components' TDP (Thermal Design Power), which represents maximum power draw under full load. Real-world average draw is usually 60-80% of TDP, but you should size for worst-case (full load) to ensure stability.
PSU Sizing Tiers
550-650W covers most mid-range gaming builds (Core i5 + RTX 3070). 750-850W is the sweet spot for high-end gaming (Core i9/Ryzen 9 + RTX 4080). 1000W+ is only needed for extreme overclocking builds or workstations with multiple GPUs. Always buy from reputable brands: Seasonic, Corsair, EVGA, be quiet!, or Super Flower.
Frequently Asked Questions
How much wattage do I need for my PC?
Add up the TDP of all components (CPU + GPU are the main draws) and multiply by 1.25 for 20% headroom. A typical gaming PC with a 65W CPU and 250W GPU needs at minimum a 400W PSU, with a 550W recommended. High-end builds with a 150W CPU and 400W GPU should use a 750-850W unit.
Why add 20% headroom to PSU wattage?
Power supplies run most efficiently at 50-80% load. Running a PSU at 100% is inefficient, causes heat, and shortens lifespan. Adding 20-30% headroom keeps the PSU in its optimal efficiency range and provides room for overclocking and future upgrades.
Does PSU efficiency rating matter?
Yes — an 80 Plus Bronze/Gold/Platinum certification means the PSU is at least 82-90%+ efficient at typical loads. A Gold PSU wastes less electricity as heat, runs cooler, and typically has better voltage regulation, protecting your components.
Should I get a modular or non-modular PSU?
Modular PSUs allow unused cables to be removed, improving airflow and making builds cleaner. Semi-modular PSUs have fixed main cables but modular peripheral cables — a good balance. Non-modular are cheapest but leave unused cables in the case.
Is this PSU calculator free?
Yes, completely free with no signup required.