PC Power Supply Calculator
Find the right PSU wattage for your build in seconds. Accounts for GPU power spikes, checks the PSU you already own and shows what your PC costs to run.
What makes this calculator different
Sized for power spikes
Graphics cards spike far above their rating for milliseconds. We model each GPU generation's spikes, so your PC won't randomly shut off mid-game.
Checks the PSU you have
Upgrading your GPU? Enter your current PSU and get a clear answer: enough, tight or too small. You'll know before you spend money on a new one.
Shows the real running cost
See what your build costs per month at your electricity rate, plus the right battery backup size and power connectors.
Power supply requirements by graphics card
Recommended wattage with a Ryzen 7 9800X3D. See every GPU →
How we calculate your wattage
- Maximum sustained load. We add your CPU's real power limit, your GPU's total board power and everything else: motherboard, memory, drives, fans, pump and RGB.
- Spike check. We multiply GPU power by a spike factor for its generation. RTX 30 cards spike hardest. RTX 40, RTX 50 and RX 9000 cards spike less.
- Headroom. We size the PSU so sustained load stays at or below 80% of its rating, then round up to a size you can buy. The minimum figure allows up to 90%.
Want the details? Read the full methodology.
Frequently asked questions
How many watts does my PC need?
Most gaming PCs need 550 to 850 W. The graphics card matters most. An RTX 5060 or RX 9060 XT build is comfortable at 550 W, an RTX 5070 Ti or RX 9070 XT at 750 W, an RTX 5080 at 850 W, and an RTX 5090 at 1000 to 1200 W. Pick your parts above for an exact figure.
Does a bigger power supply waste electricity?
No. A PSU only delivers the power your parts ask for. Modern 80+ Gold units stay efficient from about 20% to 80% load, so a slightly oversized PSU costs nothing extra to run and runs quieter.
What are GPU power spikes (transients)?
Modern graphics cards can briefly draw 1.5 to 2 times their rated power for a few milliseconds. Older power supplies can read these spikes as a fault and shut the PC off. ATX 3.0 and 3.1 units are designed to ride through them. That's why we show a separate spike figure and suggest a larger PSU if you're reusing an older one.
What is ATX 3.1, and do I need it?
ATX 3.1 is the current PSU standard. It handles power spikes better and includes a native 12V-2x6 (16-pin) cable for modern NVIDIA cards. If you're buying a new PSU, get ATX 3.1. It doesn't cost more. Read our PSU guide.
Why do other calculators give different numbers?
Some calculators pad every part to sell bigger power supplies. Others ignore GPU spikes entirely. We use each part's real power limits, add the spike behavior of each GPU generation, then keep the result at or below 80% load. See our full method.
Can I reuse my old power supply with a new graphics card?
Often, yes. Enter its wattage in the "Already have a power supply?" section and we'll tell you if it's enough, tight or too small. If it's more than 7 to 10 years old or has a poor reputation, replacing it is cheap insurance for expensive parts.