Motor Synchronous Speed Calculator
Calculate synchronous speed from supply frequency and pole count.
About Motor Synchronous Speed Calculator
Synchronous speed depends only on frequency and pole count. An induction motor always runs slightly slower because slip is what generates rotor current and therefore torque. A four-pole motor runs at 1,500 rpm on 50 Hz and 1,800 rpm on 60 Hz, which is why equipment moved between regions changes speed by 20 per cent.
Formula
Motor Synchronous Speed
n_s = 120 f ÷ poles
- n_s
- Synchronous speed in rpm
- slip
- Difference between synchronous and actual speed
Worked example
With the default values below, Motor Synchronous Speed Calculator returns Synchronous Speed of 1,500.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Supply frequencyminimum 1 Hz
- 50 Hz
- Number of polesaccepts 2–48
- 4
- Slip at full loadaccepts 0–100 %
- 3 %
Results
- Synchronous Speed
- 1,500.00 rpm
- Full-Load Speed
- 1,455.00 rpm
- Pole Pairs
- 2
- Slip
- 45.00 rpm
- Synchronous Speed at 60 Hz
- 1,800.00 rpm
Step by step
- 1Values used
- 2Motor Synchronous Speed
- 3Synchronous Speed= 1,500.00 rpm
- 4Full-Load Speed= 1,455.00 rpm
- 5Pole Pairs= 2
- 6Slip= 45.00 rpm
- 7Synchronous Speed at 60 Hz= 1,800.00 rpm
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation or tax into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Motor Synchronous Speed calculated?
n_s = 120 f ÷ poles Synchronous speed depends only on frequency and pole count. An induction motor always runs slightly slower because slip is what generates rotor current and therefore torque.
Why does Motor Synchronous Speed matter?
A four-pole motor runs at 1,500 rpm on 50 Hz and 1,800 rpm on 60 Hz, which is why equipment moved between regions changes speed by 20 per cent.
What values do I need to enter?
This calculator takes 3 inputs: Supply frequency, Number of poles, Slip at full load. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.