Technical calculators that show their work

Find the voltage drop in single-phase and 3-phase circuits — absolute volts, percentage, final load voltage and heat loss. Uses NEC Chapter 9 Table 8 conductor resistances.

Estimate how many BTU/h your room needs for cooling, based on floor area with documented adjustments for climate, insulation, sun, people and appliances.

Pick the smallest standard copper conductor whose ampacity covers your load current, with the ampacity margin, metric cross-section and the code caveats that apply.

Enter your daily energy consumption and get the battery bank, solar array and inverter sizes needed — with every sizing factor (DoD, autonomy, derate) explicit.

Enter driver and driven teeth to get the ratio, output speed and output torque — with the mesh efficiency and multi-stage notes spelled out.

Enter airflow and your design friction rate to get the round duct diameter, the next nominal size up, and the resulting air velocity — with the ASHRAE equation documented.

Leave exactly one field blank and the calculator solves it from the other two — and shows power as a bonus. The classic V = I × R with all its rearrangements.

Enter battery Ah and voltage, your load in watts, plus DoD and inverter efficiency, to get realistic runtime — not the naive Ah ÷ A figure.