Wire Size & Voltage Drop Calc

Voltage drop calculator and wire size calculator for electricians, solar installers and serious DIYers. Find the minimum wire gauge for an allowed voltage drop, check the drop on the cable you already have, or see how far a run can go. Works with AWG/kcmil and mm² cable sizes, copper or aluminum, DC (12V, 24V, 48V), single-phase and three-phase circuits. Fully offline, 25 electrical calculators in one app.

CABLE
• Voltage drop: drop in volts and percent for a known conductor size
• Wire size: minimum cross section for an allowed drop
• Maximum run length: how far the cable you have will reach
• Total drop over several runs: feeder plus branch against one budget
• AWG ↔ mm² converter: both directions, exact and nearest standard size
• Conductor resistance with temperature correction
• Power loss: watts, percent and kWh per year
• Cable weight and cost: metal in an order and what it costs

POWER AND MACHINES
• Ohm's law and power: any two of volts, amps, ohms and watts
• Power triangle: active, reactive and apparent power with line current
• Power factor correction: capacitor bank in kvar and microfarads
• Motor current and speed from the nameplate
• Transformer: winding currents and turns ratio
• Load summary: a list of loads added into one demand
• Running cost of a load per day, month and year

CIRCUITS AND SITE
• Star and delta values: line against phase voltage and current
• Neutral current for three unbalanced phases
• Voltage unbalance from three measured voltages
• Reactance and impedance: series R, L and C at one frequency
• Series and parallel resistors, capacitors and inductors
• Small circuits: star-delta conversion, voltage divider, LED resistor
• Battery runtime: amp hours to kilowatt hours and hours of load
• Solar string voltage corrected for the coldest morning
• Conductor temperature worked back from a resistance measurement
• Unit conversions: kW and horsepower, watt hours, amp hours

WHY ELECTRICIANS USE IT
• Works offline, in a basement or on a roof with no signal.
• AWG/kcmil and metric mm² are two separate size series, so you get real sizes like 1.5, 2.5, 4 and 6 mm², not converted odd numbers.
• Sizes always round up to the larger conductor.
• Every result shows its formula and assumptions: resistivity, temperature, power factor, reactance and parallel runs.
• Verdicts compare against typical limits, so you can judge the result yourself.
• Charts show how the drop changes with length and size.
• Save runs into projects and reopen them with every input restored.
• Dark theme and 76 languages.

PRO, ONE-TIME PURCHASE
All calculators and the reference stay free. An optional one-time Pro purchase, with no subscription, adds:
• No ads of any kind
• PDF calculation reports to hand to a client
• CSV export of saved runs
• More than 10 saved runs
• Five extra accent colour themes

IMPORTANT
Results come from physical formulas and are estimates. They do not replace your local wiring rules, and the app does not recommend circuit breaker or fuse ratings. The final decision belongs to a qualified electrician.

Recent changes:
New: optional one-time Pro — no ads, PDF reports, CSV export, colour themes. Smoother ads and fixes.