VD = 2 × K × I × L ÷ CMThe calculator expects one-way distance and applies the return-path factor of two.
Free US electrical calculators
Wire size and voltage drop, connected.
Estimate a minimum AWG conductor for a selected voltage-drop limit, then check the voltage expected at the load. Use copper or aluminum inputs for DC, single-phase and balanced three-phase circuits.
✓ AWG 14 through 4/0✓ One-way distance✓ No signup
Choose the calculation
Two tools.
Two different answers.
Start with the question you need to answer. Wire size estimates a gauge from a drop limit; voltage drop checks the loss for a gauge you already selected.
01 · AWG SELECTION
Wire Size Calculator
Enter system voltage, load current, one-way distance, conductor material, phase and maximum drop. Get the next listed AWG that meets the simplified voltage-drop calculation.
Calculate wire size →02 · LOAD VOLTAGE CHECKVoltage Drop Calculator
Enter an existing AWG size with voltage, current, distance, conductor and phase. Get volts lost, percentage loss and estimated voltage remaining at the load.
Calculate voltage drop →Power and current conversions
These convert known electrical values. They do not select a breaker, conductor, transformer or code-compliant installation.
Know the circuit type
How do single-phase and three-phase formulas differ?
VD = √3 × K × I × L ÷ CMThe balanced three-phase estimate uses the square-root-of-three multiplier.
Reference charts & formulas
Electrical field guides & wire charts.
Inspect circular-mil area tables, distance comparisons, copper vs. aluminum resistance constants, and 60°C–90°C ampacity limits alongside the calculators.
Wire size formula →AWG circular mil chart →Wire size by distance →Maximum wire length →12V vs. 24V vs. 48V wire →Copper drop chart →Aluminum drop chart →Ampacity vs. voltage drop →60°C / 75°C / 90°C columns →Conductor derating →Cable size vs. AWG →3-phase drop formula →Single-phase formula →3% vs. 5% targets →Motor starting drop →
Electrical calculator FAQ
Use the result responsibly.
Which calculator should I use first?+
Use Wire Size when you know voltage, current, length and maximum drop but need an AWG estimate. Use Voltage Drop when you already know the conductor size and want to estimate voltage loss.
Do these calculators confirm NEC compliance?+
No. They perform simplified voltage-drop calculations and do not confirm ampacity, breaker size, derating, terminals, conduit fill or compliance with any specific edition or jurisdiction.
Can I calculate copper and aluminum conductors?+
Yes. Both tools provide a conductor-material selection and apply the configured resistance constant for the chosen material.