Convert encoder PPR to RPM: enter the pulse frequency in pulses per second and the encoder’s pulses per revolution, or solve for frequency or PPR.
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PPR To RPM Formula
Use a consistent measurement basis. Here PPR means single-channel cycles per encoder revolution before decoding. PPS can mean channel cycles/s or decoded counts/s: use D = 1 for a single-channel frequency, or D = the selected decoding multiplier for decoded counts. Include the speed ratio (SR) between the desired output shaft and encoder shaft.
- Where RPM is the revolutions per minute of the shaft you want
- PPS is the measured channel-cycle or decoded-count rate per second, matching the selected basis
- PPR is single-channel cycles per encoder revolution before decoding; datasheet PPR/CPR terminology varies. D = 1 for channel-cycle frequency, or ×1, ×2, or ×4 for decoded counts
- SR is the speed ratio = (RPM you want) ÷ (encoder-shaft RPM). For a 12:1 reduction gearbox: if the encoder is on the output and you want motor/input RPM, SR = 12; if the encoder is on the motor/input and you want output RPM, SR = 1/12.
Multiply the measured rate by 60, divide by PPR × D to obtain encoder-shaft RPM, then multiply by SR. Frequency-limit comparisons must use the same channel-cycle or decoded-count basis. A blank optional limit omits that check.
| Pulses Per Second (PPS) | Revolutions Per Minute (RPM) |
|---|---|
| 1 | 0.060 |
| 5 | 0.300 |
| 10 | 0.600 |
| 20 | 1.200 |
| 50 | 3.000 |
| 60 | 3.600 |
| 100 | 6.000 |
| 200 | 12.000 |
| 300 | 18.000 |
| 500 | 30.000 |
| 600 | 36.000 |
| 800 | 48.000 |
| 1000 | 60.000 |
| 1200 | 72.000 |
| 1500 | 90.000 |
| 2000 | 120.000 |
| 2500 | 150.000 |
| 5000 | 300.000 |
| 10000 | 600.000 |
| 20000 | 1200.000 |
| * Rounded to 3 decimals. Formula: RPM = (PPS × 60 / PPR) × SR. Here PPR = 1000, D = 1 and SR = 1, so 1 PPS = 0.06 RPM. | |
What is PPR?
Definition:
Pulses Per Revolution (PPR) is a value used to describe the resolution of some types of rotary encoders (especially incremental encoders). An encoder is a device that converts mechanical motion into electrical signals. Rotary encoders are used as feedback devices in many applications, such as machine tools and robotics.
PPR is the number of output pulses produced for one full revolution of the encoder shaft. For example, if an encoder has 100 PPR, then it produces 100 pulses for each full revolution. A higher PPR generally provides finer position/speed measurement resolution, though overall accuracy also depends on the mechanical setup, alignment, and tolerances.
Linear distance is not inherently determined by PPR alone. To convert rotation to linear travel, you must know the circumference of the wheel/pulley (and any belt/gear ratios). For example, if an encoder is attached to a wheel with a 1-meter circumference, then one wheel revolution corresponds to 1 meter of travel; a 100 PPR encoder would then produce 100 pulses per meter in that specific setup.
Incremental rotary encoders are used in situations where speed or position needs to be measured precisely over time. In machine tools and robots, for example, high-resolution encoders can track small changes in position or speed very accurately over long periods of time.
How to Calculate RPM from PPR?
Example Problem:
The following example outlines the steps and information needed to calculate RPM from PPR.
First, determine the channel cycles received in 1 second. Here PPS = 4 Hz and D = 1; the example uses a single-channel frequency, not an ×2/×4 decoded count rate.
Next, determine the PPR. The PPR for this example is 50.
Next, determine the speed ratio (SR) between the shaft whose RPM you want and the encoder shaft. In this example, assume a 12:1 reduction gearbox and the encoder is mounted on the gearbox output shaft, but you want the motor/input RPM. In that case, the motor rotates 12 times for each output revolution, so SR = 12.
Finally, calculate the RPM using the formula above:
RPM = (PPS × 60 / PPR) × SR
RPM = (4 × 60 / 50) × 12
RPM = 57.6
