How the PSU Calculator Works

The calculator adds up the power each part of your PC can draw, using its manufacturer's power specs, then rounds up to a common PSU size with some margin on top. The result is a planning estimate for a desktop PC with one graphics card. It isn't a measurement of your system.

How to Use It

Choose your CPU. This is the only required field. Each option shows its rated power and its maximum power.
Choose your graphics card, or leave it on integrated graphics.
Fill in the rest if you know it: motherboard chipset, CPU cooler, memory type and number of sticks, drives, case fans and USB devices. Anything left on "Not sure" uses the estimate shown in the list.
Press Calculate Power to see the estimated draw, a per-part breakdown and three PSU sizes.

Worked Example

A typical 1440p gaming build: Ryzen 7 7800X3D, GeForce RTX 4070 SUPER, B650 motherboard, 2 sticks of DDR5-6000, one PCIe Gen 4 NVMe drive, a 240mm AIO cooler, 3 standard case fans and 2 USB devices.

Part	Peak figure used
Ryzen 7 7800X3D (120W TDP, 162W PPT)	162W
RTX 4070 SUPER (220W board power + ~15%)	255W
B650 motherboard	75W
2 × DDR5-6000, NVMe drive, AIO, 3 fans, 2 USB devices	75W
Peak total	567W

The heavy-load estimate is 478W and idle is about 90W. Adding 20%, 30% and 50% to the 567W peak and rounding up to common sizes gives a 700W minimum, 750W recommended and 900W extra-headroom PSU, with 80 PLUS Gold or better suggested at that size. NVIDIA suggests a 650W PSU for a typical RTX 4070 SUPER system, so this calculator leans slightly conservative.

What the Results Mean

Peak power: Every part's peak figure added together, as if the CPU and graphics card both hit their limits at the same moment. Games rarely do this, but heavy rendering or stress tests can come close, so the PSU should handle it comfortably.
Heavy load (rated): The rated figures added together: CPU TDP or base power, graphics card board power, and the estimates for everything else. It's a rough guide to sustained gaming or rendering load. A CPU can sit below or above this depending on the workload and BIOS settings.
Idle: A rough estimate of the desktop sitting idle. Real idle draw depends heavily on BIOS power settings, the monitor setup and background tasks.
Minimum, recommended and extra-headroom PSU: Peak power plus 20%, 30% and 50%, each rounded up to the next common PSU size (550, 650, 750, 850W and so on). The 30% option is a sensible default. Choose the larger one if you expect to fit a more power-hungry graphics card later.
Suggested efficiency rating: A simple rule based on the recommended size: 80 PLUS Gold or better from 750W up, Bronze or better from 550W, and any 80 PLUS unit below that. It's a value suggestion, not a requirement.

Where the Power Figures Come From

Intel CPUs: Processor Base Power as the rated figure and Maximum Turbo Power as the peak, from Intel's product specifications. For example, the Core i9-14900K is 125W base and 253W maximum turbo.
AMD CPUs: TDP as the rated figure and the default package power limit (PPT, about 1.35 × TDP) as the peak. For example, the Ryzen 9 7950X is 170W TDP and 230W PPT.
Graphics cards: the reference total board power (NVIDIA calls it total graphics power) as the rated figure, plus about 15% for the peak. Factory-overclocked models from card makers often have a higher board power than the reference design.
Everything else: typical category estimates, for example 60–100W for a motherboard depending on chipset, 3–6W per case fan, 3–8W per memory stick and 5–15W per drive. They are approximations, but they rarely move the result by more than one PSU size.

The component list was last updated in November 2026. If your exact part isn't listed, pick the closest one with similar rated power.

Limitations

Short power spikes aren't modelled. Modern graphics cards can draw well above their rated power for fractions of a millisecond. PSUs built to the ATX 3.0 or 3.1 standard are designed to tolerate these excursions; older or low-quality units may shut down instead.
Overclocking and unlocked power limits. Many motherboards let CPUs run past the manufacturer's maximum power, and overclocked graphics cards draw more than reference cards. If you raise power limits, size up.
One graphics card, desktop PCs only. Multi-GPU workstations, servers and laptops aren't covered.
Monitors and speakers aren't included. They plug into the wall, not the PSU.

Your selections are sent to Orbit2x's server to run the calculation and aren't saved. See the privacy policy.

Choosing a PSU: More Than Wattage

Graphics card connectors

Check which power connectors your card uses. Many recent high-end NVIDIA cards, and a few AMD board-partner cards, use a single 12V-2x6 (formerly 12VHPWR) connector; most others need one to three 8-pin PCIe connectors. A PSU with a native cable for your card avoids adapters. Plug every connector in fully, and use separate cables rather than one split cable for high-power cards.

Efficiency ratings

80 PLUS ratings certify minimum efficiency at set loads. Efficiency affects how much extra power is drawn from the wall and turned into heat. It doesn't change how much power the PSU can deliver. The minimum efficiencies for standard desktop PSUs on 115V power are:

Rating	20% load	50% load	100% load
80 PLUS	80%	80%	80%
Bronze	82%	85%	82%
Silver	85%	88%	85%
Gold	87%	90%	87%
Platinum	90%	92%	89%
Titanium	92%	94%	90%

To estimate wall draw, divide the PC's load by the efficiency: 400W at 90% efficiency is about 444W from the wall, and at 85% about 471W. Cybenetics is a newer rating scheme that also measures efficiency and fan noise. A rating says nothing about build quality or protections, so read independent reviews of the specific model.

Size and form factor

Most cases take a standard ATX PSU. Small-form-factor cases may need SFX or SFX-L, which come in fewer high-wattage options, so check your case's specifications before you buy.

Frequently Asked Questions

Does a bigger PSU use more electricity?

No. A PSU supplies only what the PC draws, so a 1000W unit doesn't pull 1000W. Oversizing mostly costs more up front, and very large units can be slightly less efficient at the low loads a PC spends most of its time at.

What happens if my PSU is too small?

A decent PSU's over-power protection switches it off when the load is too high, so the usual symptom is the PC shutting down or rebooting during games or other heavy work. Poor-quality units may not protect themselves or the rest of the PC as well.

The graphics card maker recommends a different wattage. Which should I use?

Card makers publish a recommended system PSU that assumes a fairly power-hungry CPU. If their number is higher than this calculator's, use theirs. If it's lower, the difference comes from this calculator assuming the CPU and graphics card peak at the same time, plus extra margin.

Can my current PSU handle a new graphics card?

Enter your build with the new card. If your PSU's wattage is at or above the recommended figure, and it has the connectors the card needs, it should be fine. If it only reaches the minimum, it will probably work but with little margin, especially if the PSU is several years old.

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