The IRPF withholding applied to an employee depends not only on the employee’s salary but also on his or her personal situation.
For this purpose, the AEAT provides taxpayers with the withholdings calculator that you can find here.
The calculator does not ask for both the personal and employment data of the employee to be calculated. The percentage given by the calculator will be the one to be applied to the amount belonging to the IRPF withholding base.
It should be noted that any change in the employee’s situation or salary implies a new withholding rate, so it will be necessary to recalculate and adjust the calculations for the current year.