# Cable Voltage Drop Calculator Compute cable voltage drop from current, length, conductor size (AWG/mm²) and material, for DC, single-phase and three-phase circuits > Canonical page: https://elysiatools.com/en/tools/voltage-drop-calculator - **Category:** Math & Numbers - **Keywords:** voltage drop, cable, wire, awg, conductor, copper, aluminum, line loss, efficiency, three phase, electrical ## Overview Voltage drop is the loss of voltage along a conductor due to its resistance. Equations: - One-way resistance: R = ρ · L / A - Copper ρ = 1.68e-8 Ω·m, Aluminum ρ = 2.82e-8 Ω·m at 20 °C - DC / single-phase: Vdrop = 2 · I · R - Balanced three-phase: Vdrop = √3 · I · R - Percent drop: ΔV / Vsource · 100 - Line loss: P_loss = I² · R_total Typical limits: ≤3% for sensitive circuits, ≤5% total. AWG uses the standard copper Ω/km table, scaled for aluminum. ## Inputs - **Current (I)** (number): e.g. 15 (amps) - **One-way Cable Length (m)** (number): e.g. 30 (meters, one way) - **Conductor Material** (select) - **Size Input Mode** (select) - **AWG Size** (select) - **Cross-sectional Area (mm²)** (number): e.g. 2.5 (mm²) — used in metric mode - **Circuit Type** (select) - **Source Voltage (V)** (number): e.g. 120 or 230 ## When to use - When sizing electrical wiring for residential, commercial, or industrial installations to ensure compliance with voltage drop safety standards. - When designing long-distance power runs, such as outdoor lighting or subpanel feeds, where voltage loss is highly critical. - When comparing the performance and required thickness of copper versus aluminum conductors for a specific load. ## How it works - Select the conductor material (copper or aluminum) and choose your wire sizing mode (AWG gauge or metric cross-sectional area in mm²). - Input the circuit parameters, including the load current in amperes, the one-way cable length in meters, the source voltage, and the circuit type (DC/single-phase or balanced three-phase). - The calculator computes the total conductor resistance based on material resistivity, length, and cross-sectional area. - It applies the appropriate multiplier (2 for DC/single-phase, √3 for three-phase) to output the total voltage drop, percentage drop, and remaining voltage at the load end. ## Use cases - Verifying that a 120V branch circuit running 30 meters to a 15A appliance stays within the recommended 3% voltage drop limit. - Sizing three-phase feeder cables for industrial machinery to prevent equipment malfunction due to low voltage. - Determining the necessary wire gauge upgrade when switching from copper to more affordable aluminum conductors. ## Frequently asked questions ### What is the maximum recommended voltage drop for electrical circuits? Standard electrical codes typically recommend a maximum voltage drop of 3% for branch circuits and 5% overall from the service entrance to the farthest outlet. ### How does the calculator handle three-phase circuits compared to single-phase? For single-phase and DC circuits, the calculator multiplies the resistance by 2 to account for the return path. For balanced three-phase circuits, it applies a factor of √3 (1.732). ### Can I input wire sizes in both AWG and metric units? Yes, you can toggle the Size Input Mode between AWG wire gauge sizes and metric cross-sectional area in square millimeters (mm²). ### Does conductor material affect the voltage drop calculation? Yes, copper has lower resistivity (1.68e-8 Ω·m) than aluminum (2.82e-8 Ω·m), meaning aluminum conductors will experience a higher voltage drop for the same size and length. ### What temperature is assumed for the conductor resistivity? The calculator uses standard resistivity values measured at 20 °C (68 °F) for both copper and aluminum. ## Related tools - [Force Calculator (F = m·a)](https://elysiatools.com/en/tools/force-calculator): Compute force, mass, or acceleration from Newton's second law, with weight on Earth - [Kinetic Energy Calculator (KE = ½mv²)](https://elysiatools.com/en/tools/kinetic-energy-calculator): Compute kinetic energy, mass, or velocity from the other two, with momentum and km/h conversion - [Momentum Calculator (p = mv)](https://elysiatools.com/en/tools/momentum-calculator): Compute linear momentum, mass, or velocity from the other two, with kinetic energy and km/h conversion - [Ohm's Law and Power Triangle Calculator](https://elysiatools.com/en/tools/ohms-law-calculator): Solve for two unknowns among Voltage, Current, Resistance and Power from any two given values, with visual triangles and AC power-factor support - [Pressure Calculator & Converter (P=F/A, Pa/kPa/bar/atm/psi)](https://elysiatools.com/en/tools/pressure-conversion): Solve pressure, force, or area from P=F/A, and convert between Pa, kPa, MPa, bar, atm, psi, Torr, inHg, kgf/cm² - [Torque Calculator (τ = rF sinθ)](https://elysiatools.com/en/tools/torque-calculator): Compute torque, force, or lever arm from τ = r·F·sin(θ), with the perpendicular force component shown - [Absolute Value Calculator](https://elysiatools.com/en/tools/absolute-value-calculator): Calculate the absolute value of positive, negative, or decimal numbers and explain the sign relationship - [Adjusted R-Squared Calculator](https://elysiatools.com/en/tools/adjusted-r-squared-calculator): Calculate adjusted R squared from R squared, sample size, and predictor count ## Samples - [Web Image Processing Python Samples](https://elysiatools.com/en/samples/web-image-processing-python): Web Python image processing examples using PIL/Pillow including reading, saving, resizing, and format conversion - [Android Image Processing Java Samples](https://elysiatools.com/en/samples/android-image-processing-java): Android Java image processing examples including reading/saving images, scaling, and format conversion - [Android Image Processing Kotlin Samples](https://elysiatools.com/en/samples/android-image-processing-kotlin): Android Kotlin image processing examples including reading/saving images, scaling, and format conversion - [Web Image Processing Rust Samples](https://elysiatools.com/en/samples/web-image-processing-rust): Web Rust image processing examples including image read/save, scaling, and format conversion ## Related content - [Electrical Circuit Calculation, Power, and Cable Sizing Tools](https://elysiatools.com/en/hubs/electrical-circuit-power-and-cable-sizing): Compare Ohm's law, resistor and capacitor network math, voltage divider and cable drop calculators, electricity cost tools, and power or energy converters in one focused electrical hub. - [Audio Encoding and Format Conversion Tools](https://elysiatools.com/en/hubs/audio-convert): Compare audio format conversion, bitrate changes, sample-rate conversion, codec swaps, and export tools in one hub for delivery and archive workflows. - [Image Format Conversion and Animated Export Tools](https://elysiatools.com/en/hubs/image-convert): Compare image format converters for JPG, PNG, GIF, AVIF, WebP, TIFF, ICO, base64, and animation-friendly exports in one hub. - [JSON Interchange and Format Translation Tools](https://elysiatools.com/en/hubs/json-convert): Compare JSON conversion tools for CSV, YAML, TOML, GraphQL, XML, Markdown, Excel, BSON, EDN, and related structured formats in one hub.