VOLTAGEDROPCALCULATOR
Resistance Planning Tool

Wire ResistanceCalculator

Estimate conductor resistance from conductor size, material, temperature, and run length before you size the circuit.

Estimate conductor resistance from size, material, temperature, length, and parallel sets, then turn that resistance into a quick voltage-drop and power-loss check. This tool is intentionally grounded in DC resistance. It is useful for planning, submittal review, and troubleshooting, but final AC design should still consider impedance, power factor, raceway conditions, terminations, and code ampacity rules.

Calculator Inputs

Resistance first, voltage-drop check second

Results

Temperature-adjusted resistance estimate

Adjusted ohms / 1000 ft
1.931
Base resistance corrected from 20 C to 75 C.
Effective ohms / 1000 ft
1.931
Parallel sets applied: 1.
One conductor
0.2897 ohm
Round-trip pair
0.5794 ohm
3-phase drop factor
0.5018 ohm
Voltage-drop check
Estimated drop
11.587 V
9.66% of 120 V
Load-side voltage
108.413 V
Estimated conductor loss: 231.750 W
Circuit note
Single-phase line-to-line and line-to-neutral planning checks typically use round-trip conductor resistance.
Temperature matters

Resistance rises with conductor temperature. A quick room-temperature assumption can materially understate drop on long loaded feeders or secondary runs.

Scope limit

This page estimates conductor resistance and resistive drop only. It does not replace a full AC impedance study, fault-duty review, or NEC ampacity check.

How To Use This Tool

Start with the actual installed one-way length, choose the conductor material and size, then set a realistic conductor temperature. If parallel sets are planned, the calculator reduces the effective resistance per set. Add current and source voltage when you want the resistance estimate converted into a practical voltage-drop and watt-loss check.

1. Estimate resistance

Use the adjusted ohms per 1000 ft and one-conductor resistance outputs to verify your base planning assumptions.

2. Check the circuit model

For DC and single-phase, focus on round-trip resistance. For three-phase, use the dedicated drop factor shown here.

3. Continue into final sizing

Once resistance looks acceptable, move into the full voltage-drop and conductor sizing calculators before issuing a final design.

Related Tools

Continue from resistance planning into full voltage-drop, sizing, reference, and code pages.

Internal Link

AC Voltage Drop Calculator

Use the full AC workflow when impedance, phase, and final drop percentage matter.

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DC Voltage Drop Calculator

Apply the same conductor data to batteries, controls, and low-voltage DC runs.

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Wire Size Calculator

Move from resistance and voltage loss to a practical conductor recommendation.

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Wire Tables

Compare resistance and ampacity values across common AWG and kcmil sizes.

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NEC Standards

Review code context before turning a resistance estimate into a final design decision.