Voltage Drop Calc NEC

About this app

NEC voltage drop calculator for electricians, apprentices, and electrical engineers. Calculate voltage drop instantly using official NEC 2023 Chapter 9 data (Tables 8 and 9). Supports single-phase and three-phase circuits with copper or aluminum conductors. No internet required - works 100% offline on the job site. FEATURES: - Single-phase and three-phase calculations - 5 voltage presets: 120V, 208V, 240V, 277V, 480V - Copper and aluminum conductors: 14 AWG through 1000 kcmil - 3 conduit types: PVC, Aluminum, Steel — separate AC resistance and reactance per conduit - NEC Chapter 9 Table 9 effective impedance (Z) at power factor - Custom power factor support (default 0.85) - Voltage drop in volts and percentage - PASS/FAIL indicator based on NEC 3% recommendation - Recommends minimum wire size to meet 3% threshold - Shows voltage at load end NEC REFERENCES: - NEC 210.19(A) Info Note 4 - Branch circuit: max 3% - NEC 215.2(A) Info Note 2 - Feeder: max 3% - Combined feeder + branch: max 5% - Chapter 9 Table 8 - DC resistance at 75°C - Chapter 9 Table 9 - AC resistance, reactance, effective Z PRO FEATURES (one-time purchase): - No ads - Save calculation history - Export calculations as PDF reports - Dark theme support BUILT FOR THE JOB SITE: This app is designed by electricians, for electricians. Enter your circuit parameters, see voltage drop instantly, and get a recommended wire size - no complicated menus or unnecessary features. ACCURATE NEC DATA: All resistance and reactance values are sourced from NEC 2023 Edition, Chapter 9. Effective impedance is calculated using Z = R·cos(θ) + XL·sin(θ) per the NEC method. Always verify calculations against the official NEC code book before installation. PERFECT FOR: - Licensed electricians - Electrical apprentices - Electrical engineers and designers - Electrical contractors - DIY electrical projects - NEC code exam preparation OFFLINE & PRIVACY: - Works 100% offline - no internet needed - No account required - No data collection - Your calculations stay on your device Simplify your voltage drop calculations on the job site.

What's new: • All impedance data verified cell-by-cell against printed NEC Chapter 9 Table 9 • Separate reactance (XL) for steel conduit — previously shared with PVC/aluminum • AC resistance now per conduit type (PVC, aluminum, steel) for all 21 wire sizes • More accurate voltage drop on large feeders (250–1000 kcmil) Thanks for using ElecTools! Send feedback to support@tradetools.dev.

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1. First observed Oct 16, 2026 · 4:59 PM $0.99