Ohm's Law Current Calculator

The Ohm's law current calculator will help determine the electrical current flowing through an energized system. It can also help you design your electrical home installations. Do you want to install a new bell or maybe a new water pump? Keep reading to find out how to calculate current using Ohm's law.

We will start exploring the definition of electric current. Electric current represents the flow of electrons through a conductor. If more electrons are flowing, we will have a higher current value. The International System of Units (SI) defines the ampere ($\text{A}$) as the unit to measure electrical current.

But why do electrons move? That is because of voltage. The voltage unit is the volt ($\text{V}$), and its work consists of pushing electrons through the conductor. Conversely, conductors, like copper cables, provide friction to the electron's flow. That is called resistance, and the SI measures it in ohms ($\text{Ω}$).

The scientific world has defined Ohm's law as the relationship between current, voltage, and resistance.

Ohm's law for current

The Ohm's law arranged for getting the current is:

where:

• $I$ — Current, in amperes ($\mathrm{A}$);
• $V$ — Voltage, in volts ($\mathrm{V}$); and
• $R$ — Resistance, in ohms ($\mathrm{Ω}$);

You can also express $I$ in terms of the electrical power ($P$):

where $P$ is the power in watts ($\mathrm{W}$).

Whenever you buy equipment, you usually will see the voltage at which it has to be connected and the power it consumes. Hence, we will use Ohm's law for current to determine how much amperage it needs. You can also try our Ohm's law current calculator.

1. Find out the power consumption of the equipment. Assume we have a hair dryer of 2000 W and a 220-volt house grid.

2. Divide power by voltage as per current Ohm's law

3. The result is 9.09 amperes of current.

In case you want to build a cable extension, you can use our wire size calculator to determine the cable diameter you need.

If you are interested in learning more about the science and math of Ohm's law, you may want to visit our other tools related to this fundament of electromagnetism:

• Ohm's law calculator;
• Ohm's law resistance calculator; and
• Ohm's law power calculator.