Use this calculator for quick wire-resistance checks before moving on to voltage-drop or power-loss calculations.
Inputs
This topic also has a deeper guide and a printable reference pack, so you can move from the live answer into the method, assumptions, and worked examples without leaving the topic cluster.
A denser practical sheet covering resistor combinations, divider outputs, LED resistor selection, voltage drop, and cable resistance in one workflow-oriented pack.
A practical field guide for low-voltage cable runs, voltage drop, line resistance, and quick sizing checks, designed for installation and bench planning rather than classroom-only use.
These are the main values the calculator uses. Keep the units consistent and, where relevant, match the assumptions explained in the related guide.
Choose the conductor material whose resistivity best matches the wire being estimated.
Unit: m
Enter the conductor length used in the resistance estimate, keeping one-way versus loop assumptions clear.
Unit: mm^2
Use the conductor cross-sectional area in square millimetres as stated for the cable.
Use this page when you need an approximate wire resistance from conductor material, length, and cross-sectional area.
The main result is the estimated conductor resistance. The supporting value shows the material assumption used in the calculation.
A longer conductor increases resistance, while a larger cross-sectional area reduces it. That is why cable size matters so much in voltage-drop and heating checks.
This estimate uses standard resistivity at room temperature. Real resistance changes with temperature, strand construction, and manufacturing tolerance.
Actual conductors warm up in use and may have different construction or manufacturing tolerance, so the real value can shift from the room-temperature estimate.
Calculate the voltage dropped across a resistance from the current and resistance values you enter.
Solve for voltage, current, or resistance from any two values and validate all three when you already have a full set of measurements.
Solve power, voltage, or current from the other two values using the core electrical power relationships.
Add resistor values in series to find the total equivalent resistance for a simple chain of components.