Ohm's Law Calculator

• •Use the Ohm's Law Calculator to check your hand calculations on homework or exam problems — comparing its result with your own working helps identify arithmetic errors before they propagate.
• •Use it during the early design phase to rapidly iterate on parameters and narrow down feasible configurations before committing time to detailed finite element simulations or full design packages.
• •Use it when reviewing a colleague's calculation or checking a vendor's data sheet for plausibility — a quick sanity check can prevent costly downstream errors.
• •Use it to generate reference data for a technical report or presentation without manual computation, ensuring consistent, reproducible numbers throughout the document.
• •Use it in the field when a quick estimate is needed and a full engineering software package is not available.

The Ohm's Law Calculator is a precision engineering calculation tool designed for students, engineers, and technical professionals. Solve for V, I, or R; compute power; combine resistors in series/parallel; decode resistor color bands All calculations are performed using established engineering formulas from the relevant scientific literature and standards. Follow the units printed beside each field. Where a unit selector is provided, the selected unit is converted internally. Results are computed in your browser without sending data to a server, which keeps your inputs private. This calculator is intended as a supplementary tool for learning and design exploration; always verify results against authoritative references for safety-critical applications.

Ohm's law V = I·R is the fundamental relationship for linear resistive circuits, stating that voltage across a resistor equals the current through it times its resistance. The three forms (V = IR, I = V/R, R = V/I) allow solving for any quantity given the other two. Power dissipated in a resistor follows P = V·I = I²·R = V²/R. For resistors in series, total resistance is R_series = R₁ + R₂ + R₃ + ..., and the same current flows through each with voltages dividing proportionally to resistance. For resistors in parallel, 1/R_parallel = 1/R₁ + 1/R₂ + ..., with the same voltage across each and currents dividing inversely with resistance. These rules enable analysis of complex resistive networks through repeated series-parallel simplification. Kirchhoff's Current Law (KCL): current into a junction equals current out. Kirchhoff's Voltage Law (KVL): sum of voltage drops around any loop equals zero. Together with Ohm's law, these form the foundation of circuit analysis. The calculator handles Ohm's law for single resistors, series/parallel combinations, power calculations, and resistor color code decoding for through-hole components.

• •Circuit design and debugging: compute required resistor values, verify component ratings, and debug unexpected voltages or currents.
• •LED current limiting: calculate the series resistor needed to drive an LED from a supply voltage with specified current (e.g., 20 mA through a 2V red LED from a 5V supply requires R = 150Ω).
• •Power dissipation check: verify that resistors in a design have sufficient wattage rating to handle actual power dissipation (I²R) plus safety margin.
• •Wire gauge selection: minimum wire size for an electrical run depends on current capacity and voltage drop, both governed by Ohm's law and wire resistance per length.
• •Resistor color code reading: convert band colors to resistance value for through-hole components still common in discrete-component designs.