Psu Watt Calculator
Picking a power supply starts with one number: how many watts your parts actually draw. Enter your CPU and GPU (or pick them from the preset list), add your other components, and this PSU watt calculator estimates total system load, recommends a PSU wattage with 25% headroom, and shows what that costs to run per year.
Estimates use max board power for presets (CPU turbo power, GPU board power). Motherboard is counted at 80W, each RAM module at 3W, each drive at 10W, each fan at 5W. Recommended PSU = load × 1.25, rounded up to the next 50W.
Worked example, verified against the tool
A build with an Intel i7-14700K (219W), an RTX 4070 Super (220W), 2 RAM modules, 2 drives, 4 fans, 50W of peripherals, and no overclock: 219 + 220 + 80 + 6 + 20 + 20 + 50 = 615W estimated load. With 25% headroom (615 × 1.25 = 768.75) the tool recommends an 800W PSU, which would run at about 77% load at full tilt.
How the estimate works
The tool adds up worst-case draw per part, then adds headroom:
| Component | How it is counted |
|---|---|
| CPU | Turbo/max power you enter (presets use published board power) |
| GPU | Board power per card × number of cards |
| Motherboard | 80W baseline |
| RAM | 3W per module |
| Storage | 10W per SSD/HDD |
| Fans | 5W per fan |
| Overclock | Optional +10/20/30% on CPU + GPU only |
Recommended PSU = estimated load × 1.25, rounded up to the next 50W. The 25% headroom covers transient power spikes (modern GPUs can spike well above their rated board power for milliseconds), capacitor aging, and future upgrades.
Choosing the right PSU, not just the right wattage
Wattage is the headline, but efficiency and quality decide the running cost and reliability:
| 80 Plus rating | Efficiency at 50% load (115V) |
|---|---|
| Standard | 80% |
| Bronze | 85% |
| Silver | 88% |
| Gold | 90% |
| Platinum | 92% |
| Titanium | 94% |
PSUs are most efficient near 50% load, which is a second reason for the headroom: a 615W peak on an 800W unit means typical gaming loads of 400-500W land right around the efficiency sweet spot instead of pinned at the top of the range. Do not oversize wildly, though: a 615W load on a 1600W PSU idles in the inefficient low-load region and wastes money twice (purchase price and electricity). Buy from established makers (Seasonic, Corsair, be quiet!, Super Flower and similar) and check professional reviews, because a cheap no-name "800W" unit may not deliver 800W on the 12V rail where it counts.
What competing calculators miss
The well-known PSU calculators either demand that you already know every part's wattage (Cooler Master) or bury you in sub-menus (OuterVision). None gives you one-click CPU/GPU presets with real board-power figures, none shows your load percentage on the recommended unit, and none estimates the yearly electricity cost. This tool does all three: pick your parts from the preset list, see the recommended wattage with headroom math shown, and optionally price the running cost at your local electricity rate.
Frequently asked questions
How many watts do I need for a gaming PC?
Most single-GPU gaming builds land between 400W and 700W of estimated load, which maps to 550W to 1000W PSUs after headroom. Enter your exact parts above for a precise figure.
Is a 650W PSU enough for an RTX 4070?
Usually yes: an RTX 4070 Super (220W) with a mid-range CPU totals roughly 450-550W of load, so a quality 650W unit with 25% headroom covers it. Check the tool with your CPU.
What happens if my PSU wattage is too low?
Expect shutdowns or reboots under load, especially during GPU transient spikes. In the worst case, an overloaded cheap PSU can fail and damage components. Size with headroom.
What does 80 Plus Gold mean?
It certifies at least 87-90% efficiency at typical loads (higher is better). A Gold unit wastes less electricity as heat than a Bronze unit at the same wattage.
Should I buy a bigger PSU for future upgrades?
One step up (e.g. 850W instead of 750W) is reasonable future-proofing. Three times your load is not: efficiency drops at very low loads and you pay for capacity you never use.
Does overclocking change the PSU I need?
Yes. Use the overclock headroom option: heavy CPU+GPU overclocks can add 20-30% to core power draw, which often pushes the recommendation up one PSU size.
How much does it cost to run my PC per year?
Enter your electricity price per kWh and daily hours above. The estimate assumes full load; real gaming loads are typically 50-80% of that, so treat it as an upper bound.