Power ยท Torque ยท Speed Conversions
Learn HP-torque relationship, motor sizing, and power calculations
Torque in lb-ft equals HP ร 5,252 / RPM, where 5,252 is the constant derived from the definition of horsepower (33,000 ft-lb/min) divided by 2ฯ. This relationship is fundamental for selecting motors, engines, and power transmission equipment.
The constant 5,252 is where the horsepower and torque curves cross on a dynamometer chart. It equals 33,000 ft-lb/min (one HP) divided by 2ฯ, and represents the exact RPM where 1 HP produces 1 lb-ft of torque.
For 460V three-phase motors, full load amps is approximately HP ร 1.25 for standard efficiency motors per NEMA MG-1. The calculator provides electrical estimates including locked rotor current for motor starter and cable sizing.
Standard NEMA premium efficiency motors range from 90-96% depending on size, with larger motors having higher efficiency. Motor efficiency affects the actual power consumption and heat generation, which is critical for compressor station electrical and cooling design.