Estimate US AWG size or an IEC/UK–EU metric cross-section for voltage-drop planning.
✓ Reviewed July 26, 2026◇ Runs locally○ No sign-up
United States / AWG preliminaryPreliminary engineering estimate
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Enter values and calculate.
APPLICABILITY
Where this result fits
Region
United States / AWG preliminary · IEC / UK–EU metric preliminary
Result type
Preliminary engineering estimate
Standards basis
NFPA 70 — National Electrical Code; IEC 60364-5-52:2009 + AMD1:2024 — Wiring systems
Edition / version
NFPA 70 (NEC) 2026 reference; IEC 60364-5-52:2009 + AMD1:2024; BS 7671:2018+A3:2024 / A4:2026 transition to 15 October 2026
Important: The US mode uses a limited 60°C planning table; the metric mode sizes for resistive voltage drop only. Neither is a permit or final cable-selection calculation. A qualified electrician must verify the complete installation. Electrical safety policy →
STEP BY STEP
How to use the Wire Size Calculator
Choose United States NEC/AWG preliminary or IEC/UK–EU metric preliminary mode.
Enter design current, a 120/240 V or 230/400 V preset, one-way distance, material, phase, and voltage-drop limit.
In metric mode, set an estimated conductor temperature for resistance correction.
Treat the result as a planning check, then verify ampacity, correction factors, protection, terminals, installation method, adopted edition, and local rules with a qualified electrician or engineer.
ACCURACY & LIMITS
What to know before using the result
The US mode uses a limited 60°C AWG planning table and is not a complete NEC calculation.
The metric mode calculates resistive voltage drop only and intentionally does not reproduce IEC or BS 7671 ampacity tables; national selection and professional verification remain required.
HELP
Frequently asked questions
How accurate is the Wire Size Calculator?
The calculator uses the formula shown on this page and keeps full numeric precision internally before formatting the result. The US mode uses a limited 60°C AWG planning table and is not a complete NEC calculation.
Does the Wire Size Calculator upload my input?
No. The calculation or processing runs locally in your browser. UtiliNest does not receive or store the values you enter.
Can I use the Wire Size Calculator on a phone?
Yes. The inputs, result controls, and explanatory content are designed for current mobile and desktop browsers.
Where does the Wire Size Calculator apply?
Applicability: United States / AWG preliminary, IEC / UK–EU metric preliminary. Result classification: Preliminary engineering estimate. The US mode uses a limited 60°C planning table; the metric mode sizes for resistive voltage drop only. Neither is a permit or final cable-selection calculation. A qualified electrician must verify the complete installation.
SOURCES
Definitions and references
Reviewed against the references below on July 26, 2026. Links open the source publisher's website. Read the source policy →