To determine how much you need to pay to pay off your mortgage 15 years early, you would typically follow these steps:

1. Check your Mortgage Agreement:
   Review your mortgage agreement to see if there are any prepayment penalties or fees associated with paying off the mortgage early. Some mortgages have prepayment penalties, while others may allow you to make additional payments without penalties.
2. Contact your Lender:
   Reach out to your mortgage lender and inquire about the process for making additional payments towards the principal and paying off the mortgage early. They can provide you with the most accurate and up-to-date information on your specific mortgage terms.
3. Calculate the Additional Monthly Payments:
   Determine how much extra you can afford to pay each month towards your mortgage. Use a mortgage payoff calculator to estimate how much you need to pay each month to have the mortgage paid off in 15 years.
4. Consider Lump-Sum Payments:
   If making monthly additional payments is not feasible, consider making occasional lump-sum payments when you have extra funds. Again, check with your lender to ensure there are no restrictions or penalties for doing so.
5. Review the Amortization Schedule:
   Ask your lender for an updated amortization schedule that reflects your extra payments. This will show you how the additional payments impact the remaining balance and help you track your progress.
6. Budget and Financial Planning:
   Ensure that making extra payments aligns with your overall financial goals and that you have a solid budget in place. It’s crucial to strike a balance between paying off your mortgage early and meeting other financial obligations.

Remember that the specific details can vary depending on your mortgage terms, so it’s essential to consult with your lender for personalized advice.