Ohm's Law Calculator

• •Use the Ohm's Law Calculator when solving homework or exam problems that require quick numerical verification of your hand calculations — instant feedback 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. Inputs support both metric (SI) and imperial unit systems, with unit conversion handled automatically — simply select your preferred unit from the dropdown next to each field. Results are computed instantly in the browser without sending data to a server, ensuring both speed and privacy. 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.