Ohm's Law Calculator
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Other tools you may find usefulOhm's Law Calculator - Calculate Voltage, Current, Resistance and Electrical Power
Calculate voltage, current, resistance or power with a simple Ohm's Law calculator. Just enter two known values and the tool will automatically determine the remaining parameters of the circuit. An indispensable helper for electronics engineers, students and engineers designing electrical systems.
Run the calculator Ohm's law See formulas and examples
What is Ohm's Law
Ohm's Law describes the relationship between voltage, current and resistance in an electrical circuit. It says that the voltage across a conductor is proportional to the current flowing through it, and the proportionality factor is the resistance. This relationship is described by the formula:
U = I × Rwhere:
U – voltage [V],
I – current [A],
R – resistance [Ω].
Variants of transformations of the formula
I = U / R
R = U/I
U = I × R
P = U × IThanks to these transformations, you can calculate any of the four quantities, knowing the other two. Ohm's Law Calculator automatically recognizes what data you have entered and presents the result in the appropriate units.
How to use the calculator
- Enter any two values from: voltage, current, resistance or power.
- Units are automatically recognized and converted (V, A, Ω, W).
- ClickCalculate- the calculator will display the missing values.
- Results are presented in full and scaled units (mV, mA, kΩ, kW).
Calculation examples
Example 1: Voltage calculation
I = 2 A, R = 5 Ω → U = 2 × 5 =10 V.
Example 2: Current calculation
U = 12 V, R = 6 Ω → I = 12 / 6 =2 A.
Example 3: Resistance calculation
U = 9 V, I = 0.3 A → R = 9 / 0.3 =30 Ω.
Example 4: Power calculation
U = 10 V, I = 2 A → P = 10 × 2 =20 W.
Units and conversions
| Quantity | Unit | Symbol |
|---|---|---|
| Voltage | volt | V |
| Current | ampere | A |
| Resistance | ohm | Ω |
| Power | watt | W |
Relationships between power and other quantities
P = U × I
P = I² × R
P = U² / RIn practice, these relationships allow you to select the system elements so as not to exceed the permissible current and power values. This helps prevent overheating and damage to components.
Practical tips
- In a series circuit, the current is the same at every point.
- In a parallel connection, the voltage is constant for all branches.
- The power loss in a resistor is the product of the square of the current and its resistance.
- The total resistance can be calculated using the series and parallel connection calculator.
Frequently asked questions (FAQ)
What are the units in Ohm's Law?
Voltage – volt (V), current – ampere (A), resistance – ohm (Ω), power – watt (W).
Does Ohm's Law apply to all materials?
No, only applies to linear materials in which the relationship between voltage and current is proportional (e.g. metals).
What does a negative voltage result mean?
A negative result indicates the opposite direction of current flow in relation to the adopted reference.
How to convert units from mA, kΩ and mV?
The calculator automatically converts units - you don't have to convert anything manually.
Summary:Ohm's Law Calculator allows you to quickly determine voltage, current, resistance or power based on two known parameters. It facilitates the design and analysis of electrical systems and helps in learning the basics of electronics.