Mortgage Overpayment Calculator 2026/27

Step 1: Baseline Mortgage: Balance = £200,000.00; Term = 25 Years; Payment = £1,111.43/month
Step 2: Add Monthly Overpayment = £200.00 (Total Monthly Payment = £1,311.43)
Step 3: Run Payoff Simulation:
        - Month 1: Interest = £200,000.00 * (0.045 / 12) = £750.00
          Standard Principal Paid = £1,111.43 - £750.00 = £361.43
          Overpayment Principal Paid = £200.00
          Total Balance Reduction = £361.43 + £200.00 = £561.43
          Ending Balance Month 1 = £199,438.57
        - Month 2: Interest = £199,438.57 * 0.00375 = £747.89 (already saving £2.11 in Month 2 interest)
Step 4: Calculate Cumulative Savings at Year 25:
        - Mortgage paid off in full after 19 Years and 8 Months.
        - Term Reduction = 5 Years and 4 Months saved.
        - Total Interest Paid with overpayment = £109,720.00
        - Total Interest Paid without overpayment = £133,429.00
        - Net Interest Saved = £23,709.00

Step 1: Baseline Mortgage: Balance = £200,000.00; Term = 25 Years; Payment = £1,111.43/month
Step 2: Apply Lump Sum Overpayment at Month 1 = £15,000.00
        New Starting Balance Month 2 = £185,000.00 (less Month 1 principal reduction)
Step 3: Run Payoff Simulation with standard monthly payments continuing:
        - Mortgage paid off in full after 22 Years and 5 Months.
        - Term Reduction = 2 Years and 7 Months saved.
        - Total Interest Saved = £19,842.00
        (Making a lump sum early has a powerful compounding effect because it reduces interest charges from day one.)

Frequently Asked Questions

Should I overpay my mortgage and how do the savings work?

Overpaying your mortgage is one of the most effective ways to reduce your long-term debt and save on interest. When you make an overpayment, 100% of that money goes directly towards reducing your principal loan balance (the actual amount you borrowed), rather than paying off interest. Because your principal balance is lower, the lender calculates interest on a smaller figure in all subsequent months, leading to compounding interest savings. Overpaying can save you thousands of pounds over the life of the loan and allow you to become mortgage-free years ahead of schedule. Before overpaying, ensure your lender allows it; most standard UK mortgages permit you to overpay up to 10% of your outstanding loan balance each calendar year without incurring Early Repayment Charges (ERCs).

What is the difference between Term Reduction and Payment Reduction?

When you make a lump-sum or recurring overpayment, lenders typically offer you two choices for how the savings should be applied:

• Term Reduction (Recommended for Max Savings): Your monthly payment remains the same, but the overall length of your mortgage term is shortened. Because you continue paying the same amount against a rapidly shrinking balance, your mortgage is paid off much faster, maximizing your interest savings.
• Payment Reduction: Your mortgage term remains the same, but your future mandatory monthly payments are recalculated and reduced. This option does not save as much interest over the long run, but it improves your ongoing monthly cash flow and financial flexibility.