Tools
NEC compliant calculators
Each one is built around a specific requirement in the National Electrical Code rather than a general-purpose formula. Every result shows the article and table it came from.
NEC 450.3Live
Transformer Fuse & Breaker Size Chart
Primary and secondary overcurrent protection up to 34.5 kV, with a pass/fail check and the code article behind every number.
Open calculatorNEC 310.16In progress
Secondary Conductor Sizing
Ampacity with ambient correction, conductor-count adjustment and terminal limits, showing which constraint decided the size.
NEC 110.24In progress
Available Fault Current
Point-by-point fault current through transformer and cable impedance, for the field marking.
NEC 220In progress
Transformer Sizing
Connected load, demand factors and continuous load rules through to the next standard kVA size.