The Cable Tray Sizing Calculator is an electrical calculator tool designed to determine the correct cable tray dimensions for electrical installations. Accurate fill ratio analysis and tray sizing per NEC, IEC 60364, and BS 7671 standards. NEC Article 392 limits fill ratios based on cable type and arrangement — single-layer or. Cable tray sizing looks simple on paper, but in real projects it affects cable safety, thermal performance, maintainability, future expansion, and inspection approval. Covers ladder tray, perforated tray, wire mesh tray, and solid-bottom tray to BS EN 61537. “ I've won two contracts this.