Motor efficiency calculator
Enter a motor's rated power, number of poles and IE efficiency class and get its nominal efficiency per IEC 60034-30-1, plus the electrical input power and losses at that rating.
How IE efficiency classes work
IEC 60034-30-1 defines nominal efficiency for line-fed AC induction motors across five classes — IE1 (Standard) through IE5 (Ultra Premium) — each one roughly cutting motor losses by about a fifth compared with the class below it. Efficiency rises with power and generally falls as pole count increases, since higher-pole (slower) motors of the same power carry more current for the same torque.
The table this calculator uses lists nominal efficiency at 50 Hz for standard frame sizes from 1.1 kW to 500 kW. A motor's actual rated power almost always lands on one of these standard sizes — the calculator finds the nearest one rather than interpolating, the same way the published table is read in practice.
IE4 and IE5 are approximated. The source table only carries published IE1/IE2/IE3 values for every rating. Until fuller IE4/IE5 data is added, this calculator estimates them as IE3 efficiency plus 1 percentage point (IE4) or plus 2 percentage points (IE5), capped at 99.5%. Treat these two classes as directional, not a substitute for a manufacturer's datasheet.
Input power and losses
Pin = Prated / η
losses = Pin − Prated
Prated is the motor's shaft output — what the table lists. Efficiency η tells you how much more electrical power you actually draw to deliver that shaft power, and the difference is heat the motor has to shed.