Practical calculators and browser tools
Free, privacy-first utilities from Mindcrew. Use the calculator suite here, or move between formatters and AI cost tools without an account.
Mortgage Overpayment Calculator
Mortgage overpayments reduce the balance faster than the normal repayment schedule, which means less future interest is charged and the loan can finish earlier. This calculator compares the current scheduled repayment path with a revised path that adds a monthly, annual, or one-off overpayment.
Enter the current mortgage balance, interest rate, and remaining term. If you know the required monthly payment, enter it directly; otherwise the calculator estimates the scheduled repayment using the same amortization formula as the main mortgage calculator.
The result shows estimated interest saved, months saved, revised payoff time, baseline payoff time, and total overpaid. It is designed for quick comparison before checking your lender terms, because many mortgage products cap annual overpayments or charge early repayment fees when limits are exceeded. Use it to test a proposed monthly habit, an annual bonus payment, or a one-off lump sum before deciding whether the saved interest is worth the reduced cash flexibility.
- Enter the current mortgage balance, interest rate, and remaining term.
- Optionally enter your required monthly payment from your lender statement.
- Add the overpayment amount and frequency to estimate interest saved, time saved, and revised payoff time.
- Interest saved
- £41,842.56
- Time saved
- 6 years, 2 months
- Revised payoff time
- 18 years, 10 months
- Baseline payoff time
- 25 years
- Scheduled monthly payment
- £1,169.18
- Total overpaid
- £45,000.00
The comparison keeps the scheduled monthly payment at £1,169.18 and adds the selected overpayment pattern until the balance is cleared.
The revised estimate repays the mortgage in 18 years, 10 months, compared with 25 years without overpayments. The final payment is adjusted to £845.96 so the balance reaches zero exactly.
Methodology and sources
Last reviewed:
The baseline uses the scheduled monthly payment to amortize the current balance month by month. If no monthly payment is entered, the payment is calculated from the balance, rate, and remaining term using the standard repayment mortgage formula.
The overpayment scenario keeps the scheduled payment unchanged and adds the selected extra payment pattern until the balance reaches zero. Interest is charged monthly on the remaining balance, and the final payment is adjusted so the simulated balance reaches exactly zero.
Assumptions
- Interest rate is assumed to stay constant for the remaining term.
- Fees, product switches, payment holidays, offset balances, and interest recalculation timing differences between lenders are not modelled.
- Early repayment charge rules and annual overpayment allowances are not applied automatically; check your mortgage offer or lender statement before overpaying.
Mortgage overpayment results are illustrative only. Your lender may apply overpayment limits, early repayment charges, or different interest timing.
Spot a methodology issue? Send a correction.
Frequently asked questions
Will overpaying always save interest?
If the overpayment reduces the mortgage balance and no offsetting fee applies, it usually reduces future interest. The exact saving depends on your rate, remaining term, lender rules, and whether early repayment charges apply.
Does this include early repayment charges?
No. The calculator shows the interest and term effect before fees. Many fixed-rate mortgages allow only a limited annual overpayment before an early repayment charge applies, so check your lender terms.
Should I enter my lender monthly payment?
Yes, if you have it. The estimated required payment is useful for comparison, but your lender payment may differ because of fees, rate timing, product rules, or previous account changes.
Other calculators
Standard
Everyday arithmetic with memory functions and full keyboard support.
Scientific
Trigonometry, logarithms, and powers, plus a graph plotter and table of values.
Mortgage
Monthly payments, total interest, and a full amortization schedule.
UK Take-Home Salary
Estimate your net pay after Income Tax, National Insurance, student loan, and pension.
Salary Sacrifice
Compare pension salary sacrifice with ordinary take-home pay after tax, National Insurance, and student loan.
Student Loan
Estimate student loan repayments for Plans 1, 2, 4, 5, and Postgraduate loans.
Loan
Repayment schedule for personal loans, car finance, and more.
Savings
Project how a lump sum and regular contributions grow over time.
Currency
Convert between currencies using a median consensus from multiple live exchange-rate sources.