120 Volts To Watts: How Many Watts Is 120 Volts?

120 volts to watts AC conversion is all about amps. How so? Well, to figure out how many watts is 120 volts, you have to multiply 120V by amps. Don’t worry; we have prepared a very easy-to-use 120 volts to watts calculator that does everything automatically. Here is a quick idea of how converting 120 volts to watts works:

  • At 1 amp, 120 volts is equal to 120 watts.
  • At 2 amps, 120 volts is equal to 240 watts.
  • At 3 amps, 120 volts is equal to 360 watts.
  • ….
  • At 20 amps, 120 volts is equal to 2400 watts.

You get the gist, right? Alright, here is the calculator that makes this conversion much easier. Just insert how many amps you are putting on 120V voltage, and you will get how many watts will this 120V circuit generate automatically:

Here’s a quick example of how this calculator works: Let’s say you want to convert 120V to watts, and you know you have a 10-amp current. You just slide the amperage slider to ‘10‘ amps and get the result:

120 volts at 10 amp current will produce 1200 watts of electrical power. Here is the calculator screenshot for this conversion:

120 vac to watts at 10 amp current
This is how you can use the calculator to convert 120V to watts at 10 amp current.

Note: 120 volts on a 1-phase AC circuit can also be abbreviated as 120 VAC. That means that 120 VAC to watts is the same as 120V to watts.

Let’s have a look at how the electric power equation is used to calculate watts from 120V voltage:

120 Volts To Watts Formula And Calculation

For every 120V to watts conversion, we use the electric power equation in this form:

Power (Watts) = Electric Current (Amps) × Voltage (Volts)

When we want to calculate how many watts is 120 volts, we just insert 120V for Voltage. Obviously, you also need to know the amps (Electric Current) to make this conversion.

Here is a quick example: Let’s say you want to know how many watts is 120 volts at 10 amp current. Look at how I insert these numbers in the formula above:

Power (Watts) = 10 Amps  × 120 Volts = 1200 Watts

Now, the 120V in the standard voltage in the US. I asked our LearnMetrics electricity expert to give us answers to most frequently asked questions for this conversion (you can use the comment section to also ask any question you want us to answer):

What Is The Maximum Wattage For 120V?

Here’s how this works: Maximum wattage obviously depends on how max. amps. And maximum amps depend on our amp breakers. For example, a 15A amp breaker allows for 12A max. current (due to the 80% NEC rule for amp breakers for continuous loads; you can read more about circuit breaker sizing here). That means that the maximum wattage for 120V on a 15A breaker is 1440 watts (12A × 120V = 1440W).

That also means you can put a 1500 watt heater on a 120V circuit if you have a 15A breaker. You will need at least a 20A amp breaker.

Here are the maximum wattages for 120V, depending on the size of amp breakers:

  • For a 15A amp breaker, the maximum 120V wattage is 1440 watts (12 amps effectively).
  • For a 20A amp breaker, the maximum 120V wattage is 1920 watts (16 amps effectively).
  • For a 25A amp breaker, the maximum 120V wattage is 2400 watts (20 amps effectively).
  • For a 30A amp breaker, the maximum 120V wattage is 2880 watts (24 amps effectively).
  • For a 40A amp breaker, the maximum 120V wattage is 3840 watts (32 amps effectively).
  • For a 50A amp breaker, the maximum 120V wattage is 4800 watts (40 amps effectively).
  • For a 60A amp breaker, the maximum 120V wattage is 5760 watts (48 amps effectively).
  • For a 90A amp breaker, the maximum 120V wattage is 8640 watts (72 amps effectively).

How Many Watts Is A 120 Volt LED Bulb?

These LED bulbs use very little electricity. They do run on 120V circuits but the amp draw is minuscule; usually about 0.1 amps (that is 100 mA) for standard 750 or 800 lumen LED bulbs.

That means that a 120V LED bulb is powered by about 12 watts (120V × 0.1A = 12W).

Do I Need To Worry About DC Or 3-Phase Current On 120V Circuits?

No, never. 120 volts is always a single-phase AC current (hence we can also abbreviate is as 120 VAC).

DC current is for batteries that have 6V, 12V, and up to 48V voltage.

3-Phase AC current usually uses 480V voltage (you will rarely see any 3-phase voltage below 300 volts).

How To Convert Other Voltages To Watts?

120V is not the only voltage. You might have a battery (6V, 12V, 24V, 48V) or other standard single-phase AC voltage (110V, 115V, 208V, 220V, 240V, and so on). If you want to convert any volts to watts, you can use this general volts to watts calculator.

As always, if you have any questions about 120V to power conversion, you can use the comment below, give us some numbers, and we will solve the problem for you (and share it with everybody else).

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