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Wire Size Estimator

Who it's for: Electricians, service techs, and estimators.

Wire Size Estimator helps electricians, service techs, and estimators. turn load current, run length, conductor material into suggested conductor size range, ampacity planning note, voltage-drop reminder without hiding the assumptions behind the result.

Calculator Inputs

Next Steps

  • Use measured load amps when possible instead of nameplate assumptions.
  • Long runs and aluminum conductors can push voltage drop higher than expected.
  • If results are near the drop limit, consider one size up for margin and future load growth.

Worked Example

Example: enter realistic values for load current, run length, review suggested conductor size range, ampacity planning note, then compare the result with field conditions before using it for a material or equipment decision.

How This Calculator Works

Evaluates each available conductor size using the same resistance-based voltage-drop equations as the Voltage Drop Calculator. Selects the smallest listed gauge that meets the user-selected maximum drop percent target. Returns estimated drop, end voltage, and pass/fail status so users can compare tradeoffs quickly.

  • Evaluates each available conductor size using the same resistance-based voltage-drop equations as the Voltage Drop Calculator.
  • Selects the smallest listed gauge that meets the user-selected maximum drop percent target.
  • Returns estimated drop, end voltage, and pass/fail status so users can compare tradeoffs quickly.

Common Mistakes

  • Entering load current in the wrong unit or using an unverified field estimate.
  • Reading suggested conductor size range without checking the assumptions listed on the page.
  • Skipping manufacturer data, local code, or field verification when the result affects final installation.

FAQ

No. This is a voltage-drop-based estimator only and does not replace ampacity calculations or adopted code tables.

Yes. Longer one-way distance increases calculated voltage drop, which can require larger conductors to stay within target limits.

No. Temperature, conduit fill, grouping, and terminal limitations are not applied in this MVP estimator.

End voltage helps show practical impact at the load and makes it easier to compare conductor options before final design.

When to Call a Professional

Use a licensed electrician or engineer when the Wire Size Estimator result affects final circuit sizing, equipment protection, or code compliance.

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Kilowatts to Amps Calculator

Convert kilowatts to amps for single-phase and three-phase systems with voltage and power factor assumptions.

Conclusion

Use the Wire Size Estimator result to understand suggested conductor size range, ampacity planning note, voltage-drop reminder from load current, run length, conductor material. Keep the input assumptions with the result so another person can reproduce the same estimate.

About This Calculator

About this calculator: Electricians, service techs, and estimators.

Educational planning estimate. Verify final electrical work against applicable code, equipment data, and qualified professional judgment.

Written by BuildCalcTools Team - Wire Size Estimator methodology and field-use notes.

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