Power Supply Calculator

Martin Brinkmann
Jul 12, 2009
Updated • Dec 4, 2012

You need to be aware of a few issues if you are building your own computer system or checking out pre-configured systems. Two of the most important issues are hardware compatibility and the selection of a power supply unit that can power the computer's hardware. It is always recommended to check these out even if the computer has been assembled by a manufacturer. It is less likely that problems arise there but there have been cases where insufficient hardware has been build into a computer system causing all kinds of problems for the user.

Newegg's Power Supply Calculator is a online form that can be used to calculate a rough minimum power supply unit wattage. Many computer builders select a power supply unit that is over-dimensioned for the computer system that they are building. This is usually fueled by users on the Internet who give advice to pick a high-end power supply unit to be on the safe side.

The user has to enter data in the requested fields of the power supply calculator including information about the processor, video card, motherboard, computer memory, hard drives and optical drives. The calculator will then crunch some numbers and suggest a minimum wattage for the power supply unit.

It is always a good idea to pick a power supply unit that offers additional capacities to be on the safe side. This could be important when adding new computer hardware to the PC. It is therefor not advised to select a 400 Watt power supply unit of the calculator's suggested wattage turned out to be 396 Watt.

There are obviously other factors that play a role like picking an energy efficient power supply unit (check out the 80 plus power supply units article for pointers).

Newegg's Power Supply Calculator offers a quick calculation of the minimum wattage required for a specific computer system configuration. It is therefor a good starting point before selecting a power supply unit.

Update: The website returns a 404 not found error. You can find alternatives in the comments, or use one of the following two power supply calculators instead.


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  1. Piotr said on July 17, 2009 at 8:34 pm

    I would say that all results are too high. Due to this site my computer shouldn’t even start. Calucated value for my sys is 433Watts where my PSU is just a week 350Watts?

    ps. eXtreme Power Supply Calculator v2.5 is way more reliable.

    1. Gomer Pyle said on September 23, 2009 at 12:34 am

      Piotr is right. The eXtreme Power Supply Calculator v2.5 is the only online calculator which does not try to sell you a 100-150 Watts larger power supply than you actually need.

      1. Anto said on April 22, 2010 at 4:39 pm

        Gomer, please give me a link for extreme power supply calculator v2.5.


  2. Jojo said on July 13, 2009 at 5:53 am

    Here’s a couple of other power calculators:



  3. -bwg said on July 13, 2009 at 5:01 am

    I’ve done a number of upgrades to my Gateway 5420 including replacing the original cpu with a q6600, replacing the original HDD with a 3-drive RAID array and installing a NVIDIA GeForce 8600 GT display adapter. The motherboard is an Intel DG965OT. Egghead recommends a minimum of 509W. I’ve been running with the original 300W PSU for over a year without noticing problems.

  4. derR said on July 12, 2009 at 10:44 pm

    very old :D

    I choosed Quad Core for my i7 920
    nVidia 8800GTX for my 9800 XXX GTX+
    and 3* 2GB DDR2 RAM for my 3*2GB DDR3 RAM
    and a DVD-RW 5*7200HD

    it means i need 760W, i got 550W but I think 550W is ok or am I wrong?

  5. Grissino said on July 12, 2009 at 8:25 pm

    Ops, same comment… Hi Jonathan! ;-)

  6. Grissino said on July 12, 2009 at 8:24 pm

    It’s VERY OLD!!! You cannot calculate Phenom II needs…

  7. Jonathan said on July 12, 2009 at 8:16 pm

    Not very current…. does not even have any AMD Phenom or Phenom II CPU’s listed! Nor does it have any current video cards listed!

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