Building Wire Selector vs VoltRef Pro

Southwire's Building Wire Selector determines the minimum conductor size and the best wire and cable type for a particular installation, following the National Electrical Code® wiring methods.

VoltRef Pro is a calculator and reference set for electricians, built around the National Electrical Code. Every result cites the article it comes from and shows the steps behind it — so you can check the work instead of trusting a black box. NINE CALCULATORS • Wire Size — conductor size from load, run length, ambient temperature and bundling, checked against both ampacity and voltage drop • Voltage Drop — drop in volts and percent, with the smallest conductor that meets your target • Conduit Fill — raceway fill against the Chapter 9 limits, with the next trade size when you are over • Ampacity — Table 310.16 after ambient correction, bundling adjustment and termination temperature limits • Box Fill — required box volume tallied item by item, the way an inspector counts it • Motor Circuit — conductors at 125 %, the overload window, and the short-circuit device • Grounding — equipment grounding conductor from the device rating, grounding electrode conductor from the service • Conduit Bending — offset bend marks, multiplier and shrink • Ohm's Law — volts, amps, ohms and watts from any two SEVEN REFERENCE TABLES Ampacity (Table 310.16), conductor properties and DC resistance, raceway areas, insulated conductor areas, box fill volumes, equipment grounding, and motor full-load currents. Searchable, with copper and aluminium columns where the Code has both. SHOWS ITS WORK Derating is where branch circuits go wrong. Every ampacity result spells out the table value, the ambient correction, the bundling adjustment and the termination limit as separate lines — and the wire size result tells you which of the three actually decided the conductor. WORKS WHERE YOU DO Everything runs on device. No signal needed in a basement, a shaft, or a slab pour. High-contrast display for daylight and gloves. Save calculations to history, mark the ones you reuse as favourites, and share any result as text. FREE AND PRO Wire Size and Ohm's Law are free to use. Pro unlocks the remaining seven calculators, the full reference library and unlimited history. Pro is an auto-renewing subscription: VoltRef Pro Weekly at $1.99 per week or VoltRef Pro Yearly at $19.99 per year, each with a free trial. Payment is charged to your Apple Account at confirmation of purchase. The subscription renews automatically unless it is cancelled at least 24 hours before the end of the current period, and your account is charged for renewal within 24 hours of the end of that period. You can manage or cancel your subscription in your Apple Account settings after purchase. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://voltrefpro.volvoxmobile.com/voltrefpro/privacy IMPORTANT For planning and estimation only. Values follow the NEC as published; local amendments, the authority having jurisdiction, and equipment listings govern the installation. Always verify against the current code book before wiring. Not affiliated with, authorised by, or endorsed by the NFPA.