PSU Wattage Calculator

Choosing the right Power Supply Unit (PSU) is a capacity and compatibility decision, not just a CPU-plus-GPU addition. The PSU wattage calculator estimates the DC output capacity your selected build should plan for, includes visible allowances for the rest of the system, and shows different headroom levels. Use it to narrow the shortlist, then verify the exact graphics-card and PSU documentation before buying.

What Should a PSU Wattage Result Tell You?

A useful PSU calculator should make its assumptions visible. This page accounts for the motherboard platform, RAM, storage, fans, cooling, and optional loads instead of hiding one unexplained overhead number. It also separates a tighter estimate from a normal planning target and an upgrade-oriented scenario. That makes the result easier to audit and adjust when your build includes a second GPU, capture card, custom loop, raised power limits, or unusual USB loads.

How Does the PSU Calculator Estimate Your Build?

Select the exact CPU and GPU first, then add only the components and optional loads that you will actually run. The calculator combines the published CPU and GPU power figures with the selected component allowances and shows three scenarios: 15% headroom for a known stock configuration, 30% for general build planning, and 50% when future upgrades or uncertainty justify more capacity. The planning formula is <strong>(CPU + GPU + selected allowances) × 1.30</strong>, rounded up to a common PSU size where possible.

For example, a 120W CPU, 250W GPU, and 100W platform allowance produce a 470W base estimate; 470W × 1.30 = 611W, so 650W is the next practical planning size. If the exact GPU manufacturer specifies a 750W minimum or a different connector, use the higher valid requirement. Read the full PSU calculation methodology for the assumptions behind each allowance. This is capacity planning—not a wall-power measurement, laboratory certification, or guarantee that a particular PSU model will handle every transient event.

What to Check After Calculating PSU Wattage

• Choose the right tier: Treat the 30% result as the normal starting point for the current build. Use the 15% figure for comparison, not as an automatic buying recommendation, and use the 50% figure when a defined upgrade or unusual load justifies it.
• Apply the exact GPU requirement: Compare the result with the graphics-card manufacturer's recommended system PSU. When the documented requirement is higher, it takes priority over generic arithmetic.
• Check connectors and cables: Confirm the required PCIe 8-pin or native 12VHPWR/12V-2x6 connection, the number of cable runs, and the PSU's 12V capability. Never reuse modular cables from another PSU just because the plug fits.
• Separate efficiency from quality: 80 PLUS describes conversion efficiency at defined test points; it does not prove protections, transient behaviour, noise, temperature performance, or long-term reliability. Check independent testing of the exact model and revision.
• Plan upgrades deliberately: A larger PSU is useful when it matches a defined future GPU or expansion plan. Buying maximum wattage for an undefined upgrade can waste money and still leave you with the wrong connector or case fit.
• Diagnose symptoms correctly: An undersized or failing PSU can cause shutdowns, black screens, and reboots under load. It does not normally create a CPU/GPU-style FPS bottleneck, so investigate performance and power faults separately.