To use the Pag-IBIG online registration calculator, visit the official Pag-IBIG Fund website. You will need to input details such as your salary and the payment scheme you prefer. The calculator will provide an estimate of your contributions based on the information you provide. Remember, actual contributions may vary, so it's a good idea to consult with Pag-IBIG representatives or refer to their official resources for precise guidance tailored to your specific situation.