How does the Wire Sizing Calculator work?

Look up ampacity from tables at operating temperature Then: Calculate voltage drop: VD = (2×K×I×L) / (1000×A) for DC or single-phase Then: Select wire where VD <3% feeder, <5% combined.

Can you give an example of how to use the Wire Sizing Calculator?

Example: Input I = 100 A, L = 50 m, copper wire, assume 60°C ampacity table gives a result of AWG 6 (106 A) with ~3.1% drop, marginal (AWG 4 better choice).

Is the Wire Sizing Calculator free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Wire Sizing Calculator?

Our Wire Sizing Calculator uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

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Wire Sizing Calculator

Current (Amps)

Length (ft)

Voltage (V)

Wire sizing selects conductor diameter to limit voltage drop and prevent overheating. Code requires ampacity matching and voltage drop limits.

Symbol	Name	Unit	Description
VD	(2×K×I×L) / (1000×A) for DC or single-phase	—	(2×K×I×L) / (1000×A) for DC or single-phase
K	K value	—	Variable used in the calculation
I	I value	—	Variable used in the calculation
L	L value	—	Variable used in the calculation
A	A value	—	Variable used in the calculation
DC	DC value	—	Variable used in the calculation

Difficulty:intermediate

References

›Wire Sizing — Wikipedia

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Wire Sizing Calculator

Wire Sizing Calculator

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