Mortgage overpayment calculator
Find out exactly what a monthly overpayment saves you in interest and time. An extra hundred a month sounds too small to change anything. It usually isn't.
Updated for the 2026/27 tax year · reviewed
Your mortgage
Overpayment
Interest you'd save
£41,843
with the overpayment plan set above
Loan amount
£200,000
Monthly payment
£1,169
Time saved
6y 2m
Mortgage-free
July 2045
Total repaid with overpayments
£308,911
Total repaid without overpayments
£350,754
Total interest with overpayments
£108,911
Total interest without overpayments
£150,754
Balance over time
How the outstanding balance falls to zero, with and without the overpayment.
Repayment schedule
Overpayment is editable - change any month and everything below recalculates.
| Month | Repayment | Principal | Interest | Overpayment | Balance |
|---|---|---|---|---|---|
| Sep 2026 | £1,369 | £535.85 | £833.33 | £199,464 | |
| Oct 2026 | £1,369 | £538.08 | £831.10 | £198,926 | |
| Nov 2026 | £1,369 | £540.32 | £828.86 | £198,386 | |
| Dec 2026 | £1,369 | £542.57 | £826.61 | £197,843 | |
| Jan 2027 | £1,369 | £544.83 | £824.35 | £197,298 | |
| Feb 2027 | £1,369 | £547.10 | £822.08 | £196,751 | |
| Mar 2027 | £1,369 | £549.38 | £819.80 | £196,202 | |
| Apr 2027 | £1,369 | £551.67 | £817.51 | £195,650 | |
| May 2027 | £1,369 | £553.97 | £815.21 | £195,096 | |
| Jun 2027 | £1,369 | £556.28 | £812.90 | £194,540 | |
| Jul 2027 | £1,369 | £558.60 | £810.58 | £193,981 | |
| Aug 2027 | £1,369 | £560.92 | £808.26 | £193,420 |
- Repayment
- £1,369
- Principal
- £535.85
- Interest
- £833.33
- Overpayment
- Repayment
- £1,369
- Principal
- £538.08
- Interest
- £831.10
- Overpayment
- Repayment
- £1,369
- Principal
- £540.32
- Interest
- £828.86
- Overpayment
- Repayment
- £1,369
- Principal
- £542.57
- Interest
- £826.61
- Overpayment
- Repayment
- £1,369
- Principal
- £544.83
- Interest
- £824.35
- Overpayment
- Repayment
- £1,369
- Principal
- £547.10
- Interest
- £822.08
- Overpayment
- Repayment
- £1,369
- Principal
- £549.38
- Interest
- £819.80
- Overpayment
- Repayment
- £1,369
- Principal
- £551.67
- Interest
- £817.51
- Overpayment
- Repayment
- £1,369
- Principal
- £553.97
- Interest
- £815.21
- Overpayment
- Repayment
- £1,369
- Principal
- £556.28
- Interest
- £812.90
- Overpayment
- Repayment
- £1,369
- Principal
- £558.60
- Interest
- £810.58
- Overpayment
- Repayment
- £1,369
- Principal
- £560.92
- Interest
- £808.26
- Overpayment
You've found the interest saved. What did it cost you elsewhere?
Every pound overpaid is a pound not in your ISA or pension. Quidworth runs both paths side by side, so you can see which leaves your household better off by the time the mortgage ends.
Create your free accountHow this calculator works
We run your mortgage through the standard UK repayment formula twice: once at your normal monthly payment, and once with your overpayment added on top every month. Both scenarios use the same balance, rate and term - the only difference is the extra amount going towards the loan each month.
Because the balance falls faster with an overpayment, less interest accrues on it each month - that gap compounds over the life of the loan into the interest saved shown above. The mortgage clears entirely once the balance reaches zero, which is usually years before the original term ends.
This assumes a fixed rate and monthly compounding for the whole period, and that you keep paying the same overpayment every month without missing one. Your real lender's schedule, any overpayment allowance limits, and future rate changes will shift the exact numbers - treat this as a close estimate for planning, not a formal mortgage offer.
Questions people ask
Is it worth overpaying my mortgage?
Overpaying saves guaranteed interest at your mortgage rate - on a £200,000 loan at 5%, £200 a month saves around £42,000 of interest and clears the loan six years early. Compare that guaranteed return against what savings could earn after tax, and keep an emergency fund first.
Can I overpay without penalty?
Most UK lenders allow overpayments of up to 10% of the outstanding balance each year without an early repayment charge, but the exact allowance is in your mortgage offer. Check before making large lump-sum overpayments.
Should I overpay or reduce the term?
They amount to the same thing mathematically - paying more each month shortens the effective term. Formally reducing the term locks you in; voluntary overpayments keep the flexibility to stop if money gets tight.
Does this calculator use my real mortgage details?
It assumes a standard UK repayment mortgage with a fixed rate and monthly compounding. Your real deal may re-fix at different rates over time - treat the results as a close estimate, not a quote.
Last reviewed against 2026/27 UK rules. Projections are estimates for education, not financial advice. Understanding your projections.
More calculators
All calculatorsA calculator answers one question at a time.
The planner keeps all of them next to each other, so an overpayment you model today still shows up in the pension picture in twenty years.
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