What is voltage drop in wires?

V_drop = I × R_wire. Keep below 3% for branch circuits. Long runs need larger gauge to reduce drop.

What's the relationship between volts, amps, and watts?

Power (Watts) = Voltage (Volts) × Current (Amps). To find any value, divide or multiply: Amps = Watts/Volts, Volts = Watts/Amps.

Is AWG or metric wire gauge better?

AWG (American Wire Gauge) uses arbitrary numbers where smaller = thicker. Metric (mm²) directly indicates cross-sectional area, making calculations easier.

Wire Resistance Calculator

Convert electrical units instantly with this free wire resistance calculator.

Includes reference tables, practical applications for electronics and wiring, and bidirectional conversion.

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Last updatedMay 21, 2026How we build & check our tools

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Frequently Asked Questions

Common questions about the Wire Resistance Calculator

R = ρL/A, where ρ is resistivity, L is length, A is cross-section. Copper: 0.017 Ω·mm²/m at 20°C.

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Sources & References

International System of Units (SI): electric current, voltage and resistance

Electric current, voltage and resistance is measured in the ampere (A), volt (V) and ohm (Ω). Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.

→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for electric current, voltage and resistance, from the BIPM SI Brochure (9th edition), the defining reference for the SI.

→Source: BIPM — SI Brochure (9th ed.)

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