PC builds / Power supply planning

PSU wattage calculator

Enter your parts’ power limits to estimate a PSU size, then check connectors and fit.

Capacity to compare

750 W

600 W planned load · 750 W target with allowance

A capacity estimate. Check your parts’ requirements before buying.

The starting numbers are a worked example. Replace them with your parts’ specifications.

Use the configured maximum CPU power, including turbo. Add CPU limits together for a multi-socket system.
Use total board power for your exact card. Add board power for multiple cards; enter 0 for integrated graphics.
Add motherboard, memory, drives, fans, pumps, USB power and expansion cards. 100 W is an example allowance; replace it for your build.
Add watts for a planned upgrade only if they are not already counted above.
Enter the system PSU recommendation for your exact graphics card. Use 0 only when no minimum applies.
PC4U planning choice above the entered load. It does not model brief power spikes.

Example inputs. Changes are saved on this device.

Which power figures should you enter?

For the CPU, look up the maximum power allowed by your board settings. A processor’s base power alone may miss its turbo load. For graphics, use the exact card maker’s total board power and system PSU recommendation. A chip name alone may cover several cards with different limits.

The “all other components” entry includes the board, memory, storage, cooling and any devices powered by the PC. Add their specified maximum loads where available. Do not count a part twice. External monitors with their own wall plugs are outside the PC’s PSU load.

Start with Intel’s power supply guide for the checks beyond watts. For an overclock or a changed power limit, enter the new limits. If you cannot establish the power budget, confirm it with the component maker before choosing a PSU.

What does the result mean?

The planned load adds your CPU, graphics, other parts and planned extra load. The allowance raises that total. The target is the higher of this figure and the GPU maker’s minimum PSU requirement. The result rounds up to the next capacity in the list below.

This is a planning estimate of DC output capacity, not a measurement of gaming use or power taken from the wall. An efficiency rating does not mean you should reduce the PSU’s labelled output. Brief spikes, individual rail limits and connector ratings need their own checks. A larger wattage number alone does not establish PSU quality or compatibility.

Before you buy: four checks

  • Case fit: match the required ATX, SFX or other form factor, PSU length and cable clearance.
  • Connectors: check CPU power plugs and the exact GPU’s cable instructions, including any 12V-2x6 connection.
  • Power delivery: check the PSU’s rated rails and the component maker’s requirements for brief load spikes. This estimate does not certify ATX compliance.
  • Cables: use the cables supplied for the exact PSU, or replacements the PSU maker explicitly approves. Modular PSU cables are not universally interchangeable.

For the rest of your build, use our PC compatibility guide and build budget planner.

Method and worked example

With a 125 W CPU limit, 250 W graphics card and 75 W for everything else, the planned load is 450 W. A 20% allowance gives 540 W, rounded to a listed 550 W capacity. If the GPU maker calls for 650 W, the target and displayed capacity rise to 650 W.

Available comparison sizes are 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 1000, 1200, 1300, 1500, 1600, 1800 and 2000 W. These are comparison steps, not a list of recommended products. Above 2000 W the tool shows the target and asks you to check a specialist system design rather than invent a PSU size.

The 25% starting allowance and 100 W starting “other components” value are editable PC4U planning choices. They are not measured product data or rules from Intel. Intel’s ATX12VO design guide explains CPU, graphics and rest-of-platform power budgets and the separate issue of power excursions. Use your actual parts’ documentation for a final choice.

Common PSU questions

Can I enter any CPU or graphics card?

Yes. Enter watts from the exact part’s specifications and configured limits. This avoids relying on a fixed model list. For several CPUs or cards, add the relevant power limits together in their input. Check the GPU maker’s system minimum separately.

Does 750 W mean the PC always uses 750 W?

No. A PSU capacity is an output rating. Actual demand changes with the parts and workload. The calculator estimates capacity to compare; it does not predict an electricity bill. A wall-power meter measures a different value, which includes PSU conversion losses.

Is a 25% allowance enough for every build?

No single percentage proves that. The allowance is a planning choice. Check the CPU and GPU makers’ instructions, the exact PSU’s specifications, connectors and transient-load support. A multi-GPU workstation or heavily modified system needs a component-by-component power review.

Are my entries uploaded?

The calculator keeps entries in this browser’s local storage. Its calculation does not send them to a server. Use Reset example to replace saved entries. Print build summary gives you the current input values and result to keep with your parts list.

Method reviewed 30 October 2026.