This ohms law calculator can solve for volts, amps, ohms, and watts. Just enter any two values you have, and it automatically solves the other two using ohms law formulas. The most fundamental set of electrical formulas is known as Ohm’s Law. They describe the relationship between Ohms, Volts, Amps, and Watts. If you want to use ohms law with capacitors and inductors instead of just resistors, take a look at the capacitive reactance calculator and inductive reactance calculator.
Please enter the values you have in the calculator below, and the results will automatically update.
Understanding Ohms Law
It’s essential to have a clear understanding of Ohms Law’s variables and how they are used in electrical circuits. Once you have a clear idea of what these values are and how they work, it will be a lot easier to remember how to use ohms law. Below are descriptions of each.
Voltage is also sometimes referred to s “electromotive force” and it’s a measurement of the forces applied by electrical charges. Sometimes it’s referenced in formulas by the letter V or E. In an atom, there are protons inside the middle and electrons that orbit around it. The protons are positively charged, and the electrons are negatively charged. Opposite charges attract, and like charges repel. That means that electrons love protons and want to pull in closer together, but protons and electrons hate themselves and push each other away. The force they impose on each other is voltage, and you can measure it with a voltmeter or multi-meter.
Amperage is also known as electrical current, and it’s merely the flow of electrons. Sometimes it’s referenced in formulas by the letter A or I. Amps is a measurement of electrical flow in the same way a stream of water is measured in gallons per minute. For example, a stream of water is made of water molecules, and an electrical current is simply the flow of electrons. The electrons in the outermost layer of an atom can move between atoms. To be clear, when a bunch of electrons is flowing, we measure them in amps.
Ohms is a measure of electrical resistance to the flow of electrons. Sometimes it’s referenced in formulas by the letter R or the Greek letter omega Ω. Materials where it’s harder for electrons to flow are better resistors, but when it’s easier for electrons to flow, we say that those materials are more conductive. When you apply a voltage across a resistor, it pushes a current through it. Suppose you increase the voltage across a fixed ohms resistor, the current increases. In the same way, if you keep the voltage the same but increase the resistor’s ohms, the current in it will be lower.
Watts is a unit of electrical power. Sometimes it’s referenced in formulas by the letter W or P. Electrical power is similar to other units of power such as horsepower, where a force is multiplied by a flow. In the case of watts, you can find it by multiplying volts times amps. A useful relationship to remember is that the wattage increases by four times if you double the voltage over a resistor. If you keep the voltage the same over a resistor but double its ohms, the wattage is cut in half.
The Ohms Law Formulas
As long as you have any two of the ohms law variables, you can solve the other two. You can find the formulas to solve for each variable in the ohms law formulas below. The graphical “ohms law wheel” below is simply a re-arrangement of the two ohms law formulas, and you can derive them by using algebra.
Ohms Law Formulas: E = I * R P = I * E where: • E = Volts • I = Current (amps) • R = Resistance (ohms) • P = Power (watts)