Expert Reviewer: David Chen, PE (Professional Electrical Engineer)
This calculator is maintained and validated by certified industry experts to ensure accuracy.
The **Circuit Calculator** is an essential tool for engineers, students, and hobbyists working with fundamental electrical circuits. It quickly applies Ohm’s Law and the Power Formula to solve for any two missing variables (Voltage, Current, Resistance, or Power) when you provide the other two.
Ohm’s Law Circuit Calculator
Enter any two of the following four values to calculate the remaining two. Only positive, non-zero numbers are accepted.
Calculation Steps:
Steps will appear here after a successful calculation.
Ohm’s Law Circuit Formula
The core of this calculator relies on the fundamental relationship between Voltage, Current, Resistance, and Power.
Ohm’s Law (Voltage, Current, Resistance):
$$ V = I \times R \quad \text{and its derivatives:} \quad I = \frac{V}{R}, \quad R = \frac{V}{I} $$
Power Formula (Power, Voltage, Current):
$$ P = V \times I \quad \text{and its derivatives:} \quad V = \frac{P}{I}, \quad I = \frac{P}{V} $$
Combined Power Formulas:
$$ P = I^2 \times R \quad \text{or} \quad P = \frac{V^2}{R} $$
Variables Explained
A quick breakdown of the input fields used in the calculator:
- Voltage (V): Measured in Volts. The electric potential difference across two points. Often referred to as electromotive force (EMF).
- Current (I): Measured in Amperes (Amps). The rate of flow of electric charge.
- Resistance (R): Measured in Ohms ($\Omega$). The opposition a material offers to the flow of electric current.
- Power (P): Measured in Watts (W). The rate at which electrical energy is transferred or dissipated in a circuit.
Related Calculators You Might Need
- Capacitor Value Calculator (Low Competition Keyword)
- Inductor Energy Storage Calculator (Low Competition Keyword)
- Series & Parallel Resistor Calculator (Low Competition Keyword)
- 555 Timer Frequency Calculator (Low Competition Keyword)
What is an Ohm’s Law Circuit Calculator?
An Ohm’s Law Circuit Calculator, like the one above, is a digital utility designed to simplify the complex mathematical calculations involved in basic electrical theory. Instead of manually applying formulas for voltage, current, resistance, or power, the user only needs to provide two known values. The calculator instantly determines the remaining two, saving time and minimizing calculation errors in design and analysis.
This tool is particularly valuable during the prototyping and troubleshooting phases of electrical engineering. It helps ensure that components are correctly matched and that safety margins (like component power ratings) are not exceeded. By visualizing the relationship between the four core variables, it also serves as an excellent educational aid.
How to Calculate Voltage and Power (Example)
Suppose you have a circuit where you know the Current and Resistance. Here is the step-by-step process used by the calculator:
- Identify Known Variables: Assume Current ($I$) = 5 Amps and Resistance ($R$) = 10 Ohms.
- Solve for Voltage (V): Use Ohm’s Law: $V = I \times R$. Substitute the values: $V = 5 \, A \times 10 \, \Omega = 50 \, V$.
- Solve for Power (P): Use the combined Power Law: $P = I^2 \times R$. Substitute the values: $P = (5 \, A)^2 \times 10 \, \Omega = 25 \times 10 = 250 \, W$.
- Final Result: The missing variables are Voltage ($V$) = 50 Volts and Power ($P$) = 250 Watts.
Frequently Asked Questions (FAQ)
How many variables do I need to input?
You must input exactly two valid, positive values. The calculator needs at least two inputs to solve for the remaining two variables using the combined formulas.
What does it mean if the calculator shows an “Inconsistent Input” error?
This error occurs if you entered three or four values, and those values do not align mathematically. For example, if you enter $V=10$, $I=2$, and $R=6$. Ohm’s Law states $R$ should be $V/I = 5$, not 6. The inconsistency check is crucial for validating measured data.
What are the units for Power (P)?
Power is measured in Watts (W). One Watt is equivalent to one Joule per second, or one Volt times one Ampere.
Can I use this for AC (Alternating Current) circuits?
This calculator is based on simple Ohm’s Law and is primarily designed for DC (Direct Current) circuits or for calculating RMS (Root Mean Square) values in simple resistive AC circuits. For complex AC circuits involving capacitance and inductance, you would need a calculator that handles impedance ($Z$).