# Watt Calculator

Please input two values to derive additional results, then click the Calculate button.

## Related Converters

The watt calculator helps users calculate the amount of power or energy required for a specific task or appliance.

## How do you calculate watts?

A watt (W) is a unit of power, and you can calculate the power (in watts) using the following equation:

### Watts equation:

The equation that our watt calculator uses is as follows:

W = A × V

Where,

• W – Power (in watts)
• A – Amperes (current)
• V – Volts

## Ohm’s law:

The power equation we discussed earlier is derived from Ohm’s Law, which states that:

• It describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit.

It is named after the German physicist Georg Simon Ohm, who first formulated it. The second formula that our watt calculator uses based on Ohm’s Law, expressed mathematically as:

V = I × R

Where,

• V – Voltage (volts)
• I – Current (amperes)
• R – Resistance (ohms Ω)

### Example:

Let’s say you have a circuit, like a small electronic device, with the following information:

• Current (A): 2 amperes
• Voltage (V): 12 volts

Now, we want to find out how much power (P) this device consumes. We can use a simple formula:

P = A × V

Next, add the values into the equation and calculate:

• P = 2 amperes × 12 volts
• P = 24 watts

So, this means the device uses 24 watts of power.

## Relationship between power, voltage, current, and resistance:

You can easily calculate the values of these four variables by using Ohm’s and Watt’s equations:

• Power
• Voltage
• Current
• Resistance

If you have the values for any of these two variables, you can adjust the above equations as per your needs.

Take a moment to review the chart below, which illustrates each of these transformations for better understanding.

Calculate Formula Description
Power (P) $$P = V \times I$$ Direct measurement of voltage and current required.
Power (P) $$P = \frac{V^2}{R}$$ Voltage and resistance known. Useful for understanding power dependence on voltage and resistance.
Power (P) $$P = I^2 \times R$$ Current and resistance known. Useful for understanding power dependence on current and resistance.
Voltage (V) $$V = I \times R$$ Current and resistance known. This is Ohm's Law.
Voltage (V) $$V = \frac{P}{I}$$ Power and current known. Useful when power consumption and current are measured.
Voltage (V) $$V = \sqrt{P \times R}$$ Power and resistance known. Useful for calculating voltage when resistance limits power.
Current (I) $$I = \frac{V}{R}$$ Voltage and resistance known. This is Ohm's Law.
Current (I) $$I = \frac{P}{V}$$ Power and voltage known. Useful when power consumption and voltage are measured.
Current (I) $$I = \sqrt{\frac{P}{R}}$$ Power and resistance known. Useful for calculating current when resistance limits power.
Resistance (R) $$R = \frac{V}{I}$$ Voltage and current known. This is Ohm's Law.
Resistance (R) $$R = \frac{V^2}{P}$$ Voltage and power known. Useful for understanding resistance impact on power dissipation.
Resistance (R) $$R = \frac{P}{I^2}$$ Power and current known. Useful for understanding resistance impact on current flow.

## How many watts in 1 amp?

The power (watts) of 1 amp depends on how much electrical voltage is there. Let’s say the voltage is 120 volts, then 1 amp would be equivalent to 120 watts of power. The power depends on how strong the electricity is (voltage).