Calculator Online

Home AI Chat AI Math Solver

NEW

Tools ▾ Category ▾

Pricing Sign In

Calculator Online

Your Result is copied!

Watt Calculator

Quickly determine the power needed to run an electrical system using this simple wattage calculator.

Enter 2 values to get the other values and press the Calculate button:

Power (R):

Ω ▾

Voltage (I):

A ▾

Current (V):

V ▾

Resistance (P):

W ▾

Related

Estimate the accurate power consumption of your electronic appliances using this online watt calculator.

Understanding Watt:

The watt (W) is the SI unit of power that measures the rate of energy transfer in electrical devices. One watt is defined as one joule of energy transferred per second. Kilowatts (kW) are also commonly used, where 1 kW = 1000 W. In electrical appliances, wattage indicates how much power a device consumes per second of operation.

How To Calculate Watts Using Amps and Ohms?

Using Ohm’s law, you can calculate power in watts easily:

Watt Formula According To Ohm’s Law:

P(W) = I(A)^2 × R(Ω)

Instead of manually calculating, you can use a watt calculator for precise and fast results.

What Are Amps, Volts, And Watts?

Watts, volts, and amperes are related electrical quantities used to measure power consumption:

P = V × I
P = V² / R
P = I² × R

Volt:

Volt (V) measures the electrical potential difference between two points in a circuit.

V = I × R
V = P / I
V = √(P × R)

Ampere:

Ampere (A) measures the flow of electricity through a circuit.

I = V / R
I = P / V
I = √(P / R)

Resistance:

Resistance (R) is the opposition to current flow in a conductor.

R = V / I
R = V² / P
R = P / I²

Where:

R = Resistance
I = Current
P = Power
V = Voltage

If manual calculations are difficult, a watts calculator provides accurate results in seconds.

Example:

Suppose a resistor has a voltage of 8 V and a resistance of 10 Ω. How do we calculate its power?

Solution:

Given:

Resistance = 10 Ω

Voltage = 8 V

Using the formula P = V² / R:

P = 8² / 10

P = 64 / 10 = 6.4 W

Amps To Watts Table (120V):

The table below lists current, voltage, and corresponding power in watts for reference:

Current (A)	Voltage (V)	Power (W)
0.1	120	12
0.2	120	24
0.3	120	36
0.4	120	48
0.5	120	60
1	120	120
2	120	240
5	120	600
10	120	1200

If your appliance values are not in the table, you can either calculate manually or use an online volts-watts-amps calculator to find exact power consumption.