PSU Calculator: Find the right power supply

A PSU calculator determines how much power your PC's power supply unit (PSU) should provide. Choose a CPU and graphics card class or enter their wattages from the specifications, set your motherboard, storage, cooling and accessories, then see the recommended wattage. The calculator also shows typical gaming load, peak load and how much of the recommended power supply's capacity would be used. Everything runs in your browser, with no download or sign-up required. Nothing is saved: only your settings appear in the address bar, and you can copy the link with the Share configuration button.

Add up the peak power of all components, add a 25% margin, and round up to the next standard wattage. For example, with a mid-range CPU and graphics card: CPU 140 W plus graphics card 220 W plus motherboard 45 W plus accessories 51 W equals a peak load of 456 W. With a 25% margin, that's 570 W, rounded up to 600 W. That's exactly how the power supply calculator works; every assumption is listed further down the page.

The rated wattage is printed on the label on the side of the power supply or in the model's specifications. Enter it in the optional field for your existing power supply (100 to 3000 W). The calculator compares it with your configuration's peak load and your selected headroom, then shows one of three results: the power supply is sufficient with headroom, sufficient for peak load but without the selected headroom, or too small. For the middle result, the peak load may reach at most 90 % of the rated wattage; above that, the power supply counts as too small. The calculator does not detect your hardware; it only uses the information you enter.

That depends on the graphics card. With a mid-range CPU and graphics card, the calculator recommends 600 W; 650 W provides some headroom. With a high-end graphics card, it recommends 700 W: a 650 W power supply can still handle the 556 W peak load, but with only around 17% headroom instead of 25%. With a top-tier graphics card, the recommendation is 1000 W. Enter your components and your power supply’s wattage in the field at the bottom to see whether it is sufficient.

With a mid-range CPU and the other default settings, the calculator recommends 600 W for a mid-range graphics card (up to approx. 220 W), 700 W for an upper-mid-range card (up to approx. 320 W), 1000 W for a high-end card (up to approx. 450 W), and 1200 W for an enthusiast card (up to approx. 600 W). With an entry-level CPU and graphics card, 400 W is enough. The full table is in the Example Result section.

Check the manufacturer's specifications. For graphics cards, look for Total Graphics Power (TGP) or Total Board Power (TBP). For processors, use the highest sustained power draw rather than TDP: Maximum Turbo Power for Intel and PPT for AMD. For AMD desktop models, PPT is usually 1.35 times the TDP, so a processor with a 105 W TDP may draw around 142 W. Enter this value in the field below the CPU selection.

A buffer of 20 to 30% above peak load is common. The calculator uses 25% by default. At a peak load of 456 W, a 20% buffer gives 547 W (rounded up to 550 W), 25% gives 570 W, and 30% gives 593 W (both rounded up to 600 W). A larger buffer is worthwhile if you plan to install a more powerful graphics card later or your power supply is a few years old, as power supplies lose some capacity over time.

No, a power supply only delivers what the PC draws. It is slightly less efficient at low loads, though: according to its certification, a Gold power supply achieves at least 87% efficiency at 20% load and at least 90% at 50% load. The difference is a few watts. Power supplies are most efficient between 40% and 60% load. That's why the calculator shows your typical load relative to the recommended power supply's rated wattage.

The tiers indicate a power supply's minimum efficiency: at 50% load, it is 85% (Bronze), 88% (Silver), 90% (Gold), 92% (Platinum) and 94% (Titanium). The rest is lost as heat. A 90%-efficient power supply delivering 400 W draws around 444 W from the outlet. Gold is a good middle ground for most gaming PCs; Platinum and Titanium are more worthwhile for very long operating hours.

Power draw from the outlet is the typical load divided by efficiency. For example, a mid-range PC with a typical load of 376 W and a Gold power supply (90% efficient at 50% load) draws around 418 W. With a Bronze power supply (85%), it would draw 442 W: 24 W more, lost as heat. The calculator shows this estimate for your selected efficiency rating. For a more accurate measurement, use a power meter. As for costs, a PC running around the clock at an average of 100 W uses 876 kWh a year, costing about €263 at €0.30 per kWh. Enter your own figures in the electricity cost calculator.

Modern graphics cards can draw significantly more power than their rated wattage for fractions of a millisecond. If the power supply has too little headroom, it shuts down and the PC restarts without an error message. ATX 3.x power supplies are designed to handle these spikes of up to 200% of their rated wattage. The calculator shows this warning for graphics cards rated at 220 W or higher. If you're keeping an older power supply, consider setting the headroom to 30%.

Usually, yes. Overclocking increases power consumption faster than clock speed because voltage rises too. The calculator multiplies CPU and GPU power consumption by 1.15 for mild overclocking and 1.35 for heavy overclocking. In the high-end PC example, peak load rises from 805 W without overclocking to 903 W with mild and 1033 W with heavy overclocking. The recommended capacity remains 1200 W for mild overclocking and rises to 1300 W for heavy overclocking. With 30 % headroom, it would even be 1600 W.

This is an estimate based on stated assumptions, not a measurement. Using categories gives a conservative result; exact CPU and graphics card specifications make it more precise. It does not account for power supply quality, aging, or the actual load from your applications. Manufacturers' calculators often give very different results for the same PC because they allow for different safety margins. If in doubt, choose the next larger standard size.