Airflow & Electrical Conversion Formulas

Get accurate calculations for HVAC, electrical, and mechanical systems using the following industry-standard formulas.

Power Conversion

• Watts to BTUs:
  BTUs = Watts × 3.413

• BTUs to Watts:
  Watts = BTUs ÷ 3.413

Electrical Power Calculations

Single Phase – Resistive Load

Watts = Volts × Amps

Three Phase – Resistive Load

Watts = (V1 × A1) + (V2 × A2) + (V3 × A3) ÷ 1.732
(1.732 is the square root of 3)

Single Phase – Inductive Load (Motors)

Watts = Volts × Amps × Power Factor

Three Phase – Inductive Load (Motors)

Watts = [(V1 × A1) + (V2 × A2) + (V3 × A3)] ÷ 1.732 × Power Factor

Ohm’s Law

Use these basic electrical formulas to find volts, amps, and resistance:

• R (Ohms) = Volts ÷ Amps

• I (Amps) = Volts ÷ Ohms

• E (Volts) = Amps × Ohms

Kilowatts to Amps Conversion

DC Circuits

Amps = (1000 × Kilowatts) ÷ Volts

AC Single Phase

Amps = (1000 × Kilowatts) ÷ (Power Factor × Volts)

AC Three Phase

Amps = (1000 × Kilowatts) ÷ (√3 × Power Factor × Line Voltage)

Quick Reference Summary