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General EE Utilities

OHM'S LAW / POWER CALCULATOR

Calculate voltage, current, resistance, and power using Ohm's law. Enter any two values to solve for the rest instantly.

Enter any two of voltage, current, resistance, or power to instantly calculate the remaining values using Ohm's law and the power equation. Results update in real time with full SI prefix formatting.

Known Values (pick two)

Quick Presets

Using Formulas

Select two values above to begin

Enter Values

Calculated Results

Select two known values to calculate results

Ohm's Law / Power Wheel

VPRII × R√(P×R)P / IV × II²×RV²/RV / IV²/PP/I²V / R√(P/R)P / VVOLTAGEPOWERRESISTANCECURRENT

Formulas Used

The calculator combines Ohm's law and the power relationship to solve unknown values from any two known inputs.

\[V = I \times R\]

\[I = \frac{V}{R}\]

\[R = \frac{V}{I}\]

\[P = V \times I\]

\[P = I^2R\]

\[P = \frac{V^2}{R}\]

V = voltage (volts)
I = current (amps)
R = resistance (ohms)
P = power (watts).

Understanding Ohm's Law

Ohm's law is the foundational relationship in electrical engineering, stating that the voltage across a conductor is directly proportional to the current flowing through it: V = I × R. Discovered by Georg Simon Ohm in 1827, it remains the starting point for virtually every circuit analysis.

Combined with the power equation (P = V × I), these two relationships allow you to solve for any electrical quantity when two others are known. The "power wheel" (also called the Ohm's law wheel) organizes all twelve derived formulas into an intuitive visual reference.

Important Considerations

  • DC only: Ohm's law in its basic form applies to DC circuits. For AC circuits, impedance (Z) replaces resistance, and phase relationships between voltage and current must be considered.
  • Linear components: Ohm's law assumes a linear relationship between V and I. Semiconductor devices (diodes, transistors) are non-linear and require different analysis methods.
  • Temperature effects: Resistance changes with temperature. Metals increase resistance with heat (positive temperature coefficient), while semiconductors typically decrease.
  • Power ratings: Always verify that components are rated for the calculated power dissipation. Derate by 50% for reliable long-term operation in aerospace and defense applications.

Calpak USA's engineering team can help with circuit analysis, component selection, and power budget optimization for your electronics designs. Contact us for a design consultation.

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