Enter any two of the four electrical values — Voltage (V), Current (I), Resistance (R), or Power (P) — into this Ohm's Law Calculator, and it solves for the remaining two, with flexible unit options for each field so you can work in millivolts, kilohms, or whatever your circuit calls for.
Voltage
--
Current
--
Resistance
--
Power
--
Joteo's Ohm's Law calculator provides an efficient way to determine the relationships between voltage, current, resistance, and power in electrical circuits. Simply input any two known values to instantly calculate the remaining parameters using fundamental electrical equations.
Ohm's Law establishes that the current flowing through a conductor is directly proportional to the voltage applied across it, provided the temperature remains constant. This fundamental principle applies to resistive circuits and forms the foundation for electrical circuit analysis.
The law demonstrates a linear relationship where doubling the voltage doubles the current, assuming resistance stays fixed. Conversely, increasing resistance while maintaining constant voltage reduces the current proportionally.
The core equation expresses the relationship between three electrical quantities:
$$V = I \times R$$Where:
This formula can be rearranged to solve for any unknown variable:
$$R = \frac{V}{I}$$$$I = \frac{V}{R}$$Electrical power represents the rate of energy transfer in a circuit. By combining Ohm's Law with power relationships, we can derive several useful equations:
$$P = V \times I$$$$P = \frac{V^2}{R}$$$$P = I^2 \times R$$Where P represents power measured in watts. These formulas allow you to calculate power dissipation using any two known electrical parameters.
Consider a circuit with 12 volts applied across a 4-ohm resistor:
When designing circuits, understanding these relationships helps select appropriate components. Higher resistance values reduce current flow, which affects power consumption and component heating. Power ratings must exceed calculated values to prevent component failure.
For LED circuits, current limiting resistors prevent excessive current that could damage the LED. Calculate the required resistance using the supply voltage minus the LED forward voltage, divided by the desired current.
Ohm's Law states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance. It's expressed as V = I × R, where V is voltage, I is current, and R is resistance.
Enter any two known values (voltage, current, resistance, or power) and the calculator will automatically compute the remaining values. Make sure to select the appropriate units for accurate calculations.
The primary formulas are: V = I × R (voltage equals current times resistance), P = V × I (power equals voltage times current), P = I² × R (power equals current squared times resistance), and P = V² ÷ R (power equals voltage squared divided by resistance).
Yes, the calculator computes electrical power using the relationships P = V × I, P = I² × R, and P = V² ÷ R. Enter any two parameters and power will be calculated automatically along with the other missing values.
The calculator supports multiple units: volts/kilovolts/millivolts for voltage, amperes/milliamperes for current, ohms/kilohms/megohms for resistance, and watts/kilowatts/megawatts for power.
Ohm's Law applies to resistive circuits but may not be accurate for non-linear components like diodes, transistors, or circuits with capacitors and inductors under AC conditions. It works best with pure resistive loads.
The calculator provides highly accurate results for ideal resistive circuits. Real-world factors like temperature, component tolerances, and parasitic effects may cause slight variations from calculated values.
If you enter values that don't satisfy Ohm's Law relationships (like V=12V, I=2A, R=10Ω when it should be 6Ω), the calculator will recalculate based on the most recently entered values to maintain mathematical consistency.