At 120 volts, the voltage household extension cords are made for in the US, 1,500 watts is 12.5 amps.
Convert to
W
A
V
Use the numbers on the nameplate. If it lists amps, use those amps as printed, and if it lists volts other than 120, use those. For several things on one cord, type a sum, such as 1500 + 60.
The answer
12.5 amps
1,500 W ÷ 120 V = 12.5 A. Amps are the watts divided by the volts.
The nameplate is the label with the device’s ratings.
Compare amps with an extension cord’s rating in amps, or watts with its rating in watts.
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Watts and amps at 120 volts
Watts and the amps they draw at 120 volts
Watts
Amps at 120 V
60 W
0.5 A
100 W
0.83 A
500 W
4.17 A
1,000 W
8.33 A
1,200 W
10 A
1,500 W
12.5 A
1,800 W
15 A
Rounded to two decimal places.
More than one thing on a cord
Add up the watts of everything that will share the cord, or add up the amps, then convert the total. Check it against the rating on the cord’s tag or packaging. You can type the sum in the calculator above, such as 1500 + 800 + 60.
These numbers don’t tell you what a home’s wiring or circuits can carry. For that, ask an electrician.
Common questions
How many watts is 15 amps?
At 120 volts, 15 amps is 1,800 watts: 15 times 120.
The household voltage, the cord rating and the advice on adding up a cord’s load come from the CPSC, and the nameplate advice from Carol’s catalog and Bosch’s and Milwaukee’s manuals. Checked against published data from CPSC, Carol, Bosch and Milwaukee.
See all 6 sources
US Consumer Product Safety Commission, “Household Extension Cords Can Cause Fires” (Pub 5032): the rating on the tag, hot cords, at least 16 AWG, temporary use, cords marked for outdoor use, not through doorways
Carol (Prysmian, formerly General Cable), Cord & Cordset catalogs: September 2024 (wire and cable abbreviations, cord types, the surface printed legend) and November 2017, CAR-0084-R1117 (extension cord facts, understanding wire gauge, the extension cord selector, GFCIs)
US Consumer Product Safety Commission, Safety Alert 5123, “Portable Generator Hazards” (2021): carbon monoxide, extension cords, backfeeding, CO alarms
Bosch, 11253VSR and 11255VSR rotary hammer operating and safety instructions (2017): recommended sizes of extension cords and grounded tools
Milwaukee, 5268-21 SDS Plus rotary hammer operator's manual (2023): recommended minimum wire gauge for extension cords, grounding and double insulated tools
US Consumer Product Safety Commission, ballot vote sheet and staff package, extension cord proposed rule (January 2015): household current at nominal 120 volts AC, and UL 817's jacketed cord for outdoor extension cords
General guidance from manufacturer and standards data. Products vary, so check the label and the maker's instructions.