Working with live electrical current can be very hazardous. Testing voltage output requires working with electrical current. Do not attempt this measurement without the proper tools and safeguards.

To measure the voltage at an electrical outlet requires the use of a multimeter. Always test your test equipment for proper operation before use.

Set the multimeter to AC voltage. The markings may appear as VAC, AC V, or a V beneath a wavy line. Choose the AC voltage closest to the voltage you will measure. Standard current in home and businesses in the USA is in the range of 110 to 120 volts. Some circuits used for equipment such as dryers, air conditioners, electric stoves, ovens and other large equipment may use voltage in the range of 220 to 240 volts. These heavy-duty circuits can be identified by their non-standard outlet plugs.

While grasping the insulated portion of the probes (never touch the metal conductor during testing) place one probe into each of the two terminals. The multimeter will display the voltage.

Carefully remove the probes, being careful not to touch the metal part of the probes to anything or each other.

The voltage should typically test in the range of 108 to 121 volts for most circuits. If voltage is higher or lower, professional electrical service may be required.