SettingsSettings for this calculationUS
The appliance's rated power in watts.
Take the running wattage from the rating plate. Appliances with motors or compressors draw considerably more than this for the first moments of starting.
Current draw
12.5 A
I = P ÷ V at 120 V single phase. For a continuous load, compare the answer against 80% of the breaker rating rather than the full rating.
- Conversion factor applied
- 0.01 A per W
They open the calculator with your figures already in it
Watts to Amps Calculator (120 V): 12.5 A — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Rearranged Ohm's law: I = P / V
- NEC 210.20(A) sizes the overcurrent device at 125% of a continuous load, and 210.19(A)(1) does the same for the conductor — which is the same rule read the other way round, as the familiar 80% ceiling on the breaker rating
Inputs used
- Power (W)
- 1500
Intermediate steps
- Conversion factor applied
- 0.01 A per W
Confidence note: I = P ÷ V at 120 V single phase. For a continuous load, compare the answer against 80% of the breaker rating rather than the full rating.
What this calculation does not cover
- This is a unit conversion, not a load calculation. It gives what one appliance draws in isolation and accounts for nothing else already on the circuit, no diversity or demand factors, and no service-level total. Sizing a branch circuit, feeder or panel needs a full load calculation to the code in force where you are.
- The division treats the figure you enter as though voltage and current were in phase. On a motor, compressor, LED driver or switch-mode supply the current the supply actually has to deliver is higher than watts divided by 120, by the reciprocal of the power factor. Where the rating plate gives a VA figure, enter that one instead.
- Starting current is excluded. A motor or compressor can pull several times its running current for the first moments after switch-on, and that surge is what governs breaker curve choice and nuisance tripping. Nothing in this result reflects it.
- The arithmetic assumes exactly 120 V at the outlet. Delivered voltage sags under load and with distance from the transformer, and a constant-power load draws proportionally more current as the voltage falls. No voltage drop along the run is calculated here.
- No conductor is sized by this figure. Ampacity depends on the insulation temperature rating, ambient temperature, and how many current-carrying conductors share a raceway or cable, and the continuous-load uplift cited in the sources is not applied to the answer either. The comparison against 80% of the breaker rating is left for you to make.
Add the equipment this sizes
This result is a specification — 12.5 A — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations2
- Rearranged Ohm's law: I = P / V
- NEC 210.20(A) sizes the overcurrent device at 125% of a continuous load, and 210.19(A)(1) does the same for the conductor — which is the same rule read the other way round, as the familiar 80% ceiling on the breaker rating
Which documents these citations point at
- National Electrical Code (NFPA 70) — 210.20(A) (United States)Electrical installations — conductor sizing and protection, load calculation, wiring methods, grounding and working clearances.
A code or standard has force only where a jurisdiction has adopted it, usually with local amendments. This site holds no adoption data for any authority, so check what is in force with the authority where you build. Any section cited above without an edition should be checked against the edition in force where you build. What it would take to know.
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.
The practical question behind this conversion is almost always whether something can be plugged in where you want to plug it. Dividing wattage by 120 V gives the current, and current is what the breaker and the conductor care about. The trap is the continuous-load rule: a circuit expected to run for three hours or more is generally limited to 80% of its rating, which turns a 15 A circuit into a 12 A allowance, or roughly 1,440 W. That is precisely why a 1,500 W space heater is a nuisance on a general-purpose circuit despite appearing to fit. Note also that appliances rated in VA rather than watts are already stating volts times amps, so the VA figure is the one to divide — using the watt figure on an inductive load will understate the current the supply actually has to deliver.