How to calculate the change in entropy in a thermodynamic system?

To calculate the change in entropy in a thermodynamic system, you can use the formula S (dQ/T), where S is the change in entropy, dQ is the heat added or removed from the system, and T is the temperature in Kelvin. This formula is based on the second law of thermodynamics, which states that the total entropy of an isolated system can never decrease over time.