Watts to Amperes – Calculator with formula, table of equivalences and practical examples of electrical systems

Calculator, formula, table of equivalences, applied examples and explanation of how to calculate electrical circuits, protections, breaker and cables.

It also explains how to solve problems such as electrical overloads with examples and a step by step for quick conversions from watts to amperes with the most common power factors .

⚡What are the formulas for Watts to amp Single-phase, two-phase, three-phase and DC?

Single-phase, two-phase and three-phase (AC) formula:

Watts to Amps Formula Single Phase, Two Phase, Three Phase

Formula (DC):

Formula watts to DC amps

Where :

  • FP = This value shows the efficiency the a device is in consuming energy, in other words it shows how much real energy in watts a device consumes. If you do not know the value, you can use some reference power factor .
  • Watts = This is the actual power of electrical equipment. They are also called Watts and are a unit of power that is used to measure the amount of energy consumed by electrical equipment.
  • L-N = The line-to-neutral voltage is a data characteristic of electrical systems. Single-phase voltage is the one commonly used in home equipment. Conversion  L-N  to  L-L
  • L-L = Line-to-line voltage, is commonly used in three-phase AC systems and is information that you can find on the nameplates of each equipment. Conversion  L-L  to  L-N
  • DC = This voltage only applies to DC systems (Direct Current Systems).
  • AC = This is the value you want to find in case the load is single-phase, two-phase or three-phase or DC .

✍How to quickly convert, transform or calculate from watts to amps?

Step 1, identify formula:

Formulas from Watts to amp

Step 2, replace:

Replace the Watts, Voltage and Power Factor, if you don’t know the power factor you can use one of these common power factors.

Step 3, example:

You have a 400W, 120V (single phase) printer with a Power Factor of 0.9. What is the amperage of the printer?

Replacing the data into the single-phase watts to amperes formula:

Example of watts to amp

🎯How to calculate an electrical circuit, protections (breakers-OCP), cables and terminals?

You have the following single-phase electrical devices and you want to know what the amperage of the protection, wiring and circuit terminals is:

  1. A 1000 watt microwave oven at 120 volts
  2. A 750 watt washing machine at 120 volts
  3. A 1500 watt dryer at 120 volts

The total power of the circuit is:

1000 watts + 750 watts + 1500 watts = 3250 watts

The maximum amperage of the circuit is:

3250 watts / 120 volts = 27 amps. (formula watts to single-phase amperes)

To know what amperage capacity of the cable, breakers and terminals you need, you must know the commercial values ​​of the protections and cables:

Nominal value of protections and outlet:

Nominal value of electrical protections in amperes

Nominal value amperes of cables:

Nominal amperage of electrical cables of different types.

Taking into account that we need 27 Amperes, we go to the protection tables and take the protection amperage value immediately higher than 30A, then we go to the cable table and take the value immediately higher than the one we require at 60ºC – 30A, cable No 10AWG.

The NEC standard requires that for ampere values ​​less than 100A, cable values ​​of 60ºC be taken and for values ​​greater than 100A, cables at 75ºC be taken.

Therefore, a 30 amp protection or breaker and No 10 AWG cable is needed. The terminals must be for 30 amps and 60ºC.

The previous example is for reference because in reality the distribution of this equipment should not be done with a single circuit but with independent electrical circuits and sometimes considering 125% of the amperage, according to what the standard indicates. NEC/NFPA70.

🔥How to solve protection or breaker trip problem?

A 15 amp protection trips when a 2000 watt microwave oven is turned on. What is causing the problem?

The problem is that the power of the microwave oven is higher than the maximum amperage of the protection or breaker. The microwave oven is overloading the circuit and causing the protection to trip.

To solve the problem, you must first calculate the amperage of the microwave:

2000 watts / 120 volts x Power Factor (0.9) = 18.52 amps. (formula watts to single-phase amperes)

The breaker trips because the microwave consumes more than what the breaker is capable of protecting 18.52 greater than 15 Amps (Protection), therefore you must replace the protection with one of 20 amps.


If you change the protection, it is likely that you will also have to change the cable, this is very important because if you do not do so you may have a possible fire.

👌How do you know if electrical equipment can be connected to an electrical outlet or outlet?

Imagine that you want to buy a new two-phase (2-phase) oven that you must connect to an electrical outlet or outlet in your kitchen. The microwave oven has a voltage of 220 volts and a power of 3500 Watts.

In your kitchen there is a 220V and 15 Amp connection, to verify this you must go to the protection panel and identify the breaker.

The first thing to do is verify that the oven consumes less than 15A, which is the capacity you have in your home.

Oven amps = 3500 watts / 220 volts x Power Factor (0.9) = 17.68 amps. (formula watts to amperes two-phase )

According to the above, the oven (17, 68 Amp.) consumes more amperage than the protection of the house (15Amp.), therefore if it is installed in these conditions this protection will be triggered.

In this case, the recommendation is to change to an oven with less power and amperage or increase the capacity of the wiring and protection of the house.

⭐How do you know if a three-phase equipment or motor in an industry is working well?

You have a 3000 W three-phase motor, with a power factor of 0.85 at 460V, which when measuring current with a multimeter has 10A, is this normal for this motor?

To answer the previous question you must convert from Watts to amperes using the formula for three-phase systems:

3000 W / √3 x 460V x FP (0.85) = 4.43 Amps

The current of that motor should be 4.43 A, however, as measured it is 10A, therefore this motor has a problem and must be repaired.

🔌How do I know how many devices I can connect in an electrical circuit?

I have a 20A circuit with No. 12 AWG wiring and I want to connect the following equipment to 120V:

  1. 200W TV
  2. 300W DVD
  3. 1000 W coffee maker
  4. 900W microwave

The first thing is to add the powers: 200 + 300 + 1000 + 900 = 2400 W

Go from Watts to amperes = 2400 W / 120V x FP (0.9) = 22.2 Amperes (formula watts to amperes single-phase)

As you can see, all of these devices cannot be connected to the same circuit, because the maximum capacity is 20A, therefore the television or DVD cannot be connected to this circuit, which must be connected to another circuit.

💡How do I know how many 180 W devices I can connect in an electrical circuit?

Imagine that you have an electrical circuit with a 20 amp breaker.

Each 180 W device consumes 180 W / 120 V x FP (1) = 1.5 amps.

So you can connect 20 amps / 1.5 amps = 13 pieces of 180W equipment to the same circuit without problems.

☝Tables of equivalences of watts (Watts) to amperes

Single-phase watts to amps table

In the previous table a power factor of 0.85 is considered.

Table to transform watts into three-phase amperes

Table to transform watts into three-phase amperes

The power factor considered in the previous table is 0.85.

🥇Examples of watts to amp

Example 1, A refrigerator consumes 3000W, how many amps is it equivalent to?

If the refrigerator is connected to 120V and assuming a power factor of 0.9, the answer would be 27.78 Amps.

300W to Amp Conversion Example

The other way to convert is to perform the calculation automatically with the watts to amps calculator:

Example calculator for watts to amperes refrigerator 3000w is equivalent to 27.78A

Example 2, How many amps does a washing machine and dryer consume in 5000W?

If the dryer is connected to 220V the amperage would be 25 Amps, assuming a power factor of 0.9.

Conversion from 5000W to amp

Important! In this example, a line-to-line voltage of 220V was considered , which is why the two-phase formula was used; however, if the connection is single-phase, the single-phase formula must be used.

Example 3, How many amperes is equivalent to 8000W three-phase circular saw connected to 460V?

In this case, the three-phase watts to amperes formula is used, therefore the amperage is: 11.16 Amperes with a power factor of 0.9.


In three-phase equipment, the power factor is very important, therefore it must be verified in each equipment; if it is not available, it can be estimated with the power factor table .

👌Most common conversions:

The equivalence of 1 watts in amps:

There are several answers for this conversion depending on the type of AC or DC current, power factor etc, however the simplest answer is  0.01 Amps, for AC voltage, power factor equal to 1 and 120V voltage.

How many amps are 1000 Watts:

The simplest answer will be 8.33 Amp with an AC voltage, a power factor of 1 and a voltage of 120V.

1500 Watts how many amps are:

Like the previous 1500Watts conversion are 12.5 Amps, with an AC voltage, a fp of 1, a single phase voltage of 120V.

600 Watts to how many amps is equivalent:

They are 5 single phase AC amps, with a voltage of 120 V and a power factor of 1.

2000 Watts to how many amps is equivalent:

The equivalence is 16.67 single phase amps of 120Volt AC, a power factor of 1.

🎯Definitions of watts, amps and volts:


Amps are the flow of electricity that is measured as electric current . You can see the amps as the flow of water through a pipe. The more water passes through the pipe, the stronger the current.


Volts are used to determine how much force is needed to make electric current flow . According to the previous example, you could think of volts as the pressure imposed on the water in a pipe, which causes the force for the water to flow.

Watts (watts):

The amps multiplied by volts are the watts, which is the measure used to determine the amount of energy consumed by electrical equipment. The higher the wattage, the greater the power in watts. In terms of the example of water, watts referred to the amount of water that has been released.

Watts a amperios en español