PLC Scan Time Calculator
Calculate total PLC scan time and maximum scan frequency from input, program, output, and overhead times.
How to Use the PLC Scan Time Calculator
- Enter the input scan time from the PLC datasheet or measurement (ms).
- Enter the program execution time based on instruction count (ms).
- Enter output scan time and system overhead, then click Calculate.
Use Cases
- •Verifying PLC response time for safety systems.
- •Optimising scan times for high-speed conveyor control.
- •Sizing PLC hardware for demanding control applications.
Formula
Scan Time = Input Time + Program Time + Output Time + Overhead. Max Frequency (Hz) = 1000 / Scan Time (ms).
Frequently Asked Questions
What is PLC scan time?
PLC scan time is the time for one complete cycle: reading inputs, executing the program, writing outputs, and housekeeping. Faster scan times allow faster process response.
What is a typical PLC scan time?
Simple PLCs scan in 1–10 ms. High-speed motion controllers may scan in under 1 ms. Large programs or many I/O points increase scan time.
Is this calculator free?
Yes, all OhMyCalc calculators are completely free to use.