This mortgage overpayment calculator shows how much interest you would save by paying more than you have to, how many years it takes off, and when you would be mortgage free. On a £200,000 mortgage at 4.5% with 20 years left, overpaying £200 a month saves £22,936 in interest and clears the mortgage four years early.
It also shows what overpaying does to your loan to value, which most calculators leave out and which can be worth more than the interest saved. Nothing is asked of you before you see the numbers.
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For illustration only. Figures assume your interest rate stays the same for the full term, which is unlikely in practice, and do not account for any early repayment charges. Check your lender’s overpayment terms before you commit. Your lender may recalculate your monthly payment after an overpayment unless you ask it to shorten the term. Clever Lending is authorised and regulated by the Financial Conduct Authority (FRN 795789).
| Question | Short answer |
|---|---|
| How much can I overpay without a penalty? | Usually 10% of the balance a year on a fixed rate. Trackers and variable rates often have no limit |
| What if I go over? | An early repayment charge, usually 1% to 5%, worked out on the amount repaid or the balance depending on the lender (HSBC) |
| Reduce the term or the payment? | Reducing the term saves about twice as much interest |
| Overpay or save? | Overpay if your mortgage rate beats your savings rate after tax |
| Can I get the money back? | Not on a standard mortgage. Offset and some flexible mortgages allow it |
A £200,000 mortgage at 4.5% with 20 years left. The gap widens every year, because early overpayments have the longest time to work.
You would pay in £38,400 over that time and get £22,900 of saved interest back, plus the years at the end with no mortgage payment at all.
| No overpayment | £200 a month extra | |
|---|---|---|
| Monthly payment | £1,265 | £1,465 |
| Time to repay | 20 years | About 16 years |
| Total interest | £103,700 | £80,700 |
| Interest saved | — | About £22,900 |
Early overpayments do the heavy lifting, because they have the longest time to work. The same £200 a month started a decade from now saves a fraction of that.
Even £50 a month makes a measurable difference. On a £200,000 repayment mortgage at 4.5% with 20 years left, with the overpayment used to shorten the term:
| Extra each month | Mortgage free in | Time saved | Interest saved |
|---|---|---|---|
| £50 | 18 years 10 months | 1 year 2 months | £6,923 |
| £100 | 17 years 9 months | 2 years 3 months | £12,949 |
| £200 | 16 years | 4 years | £22,936 |
| £300 | 14 years 7 months | 5 years 5 months | £30,892 |
| £500 | 12 years 4 months | 7 years 8 months | £42,796 |
The saving grows faster than the overpayment because each pound you overpay stops being charged interest for the rest of the term. Put your own figures in the calculator above. The pattern holds at any balance or rate.
A lump sum saves more per pound when it is paid early, because it immediately cuts the balance that interest is charged on. Regular overpayments win on total impact because they keep adding up, and they are easier to keep inside the 10% allowance.
On the same £200,000 mortgage, a £10,000 lump sum today saves £13,746 and takes 1 year 6 months off if it shortens the term. If it lowers the payment instead, the payment falls by £63 a month to £1,202, and the interest saved is just £5,184. MoneyHelper gives a similar example: £5,000 off a £250,000 mortgage at 5% with 25 years left saves £11,970 and 11 months.
Almost every overpayment calculator stops at interest saved. What they miss is what overpaying does to your loan to value, which is often the bigger number. Lenders price in bands, usually at 60%, 75%, 80%, 85% and 90%, and crossing a boundary can move you onto a better rate, often by a quarter to half a percentage point.
| Before | After a £5,000 overpayment | |
|---|---|---|
| Balance | £245,000 | £240,000 |
| Loan to value | 81.7% | 80.0% |
| Rate band | 85% | 80% |
| Worth over a five year fix | — | Around £6,000 |
Say your home’s worth £300,000 and you owe £245,000. That’s 81.7%, so you’re priced in the 85% band. Overpay £5,000 and you’re at £240,000, which is exactly 80% and a cheaper band. Half a percentage point on £240,000 is around £1,200 a year, so on a five year fix that £5,000 could be worth roughly £6,000, on top of the interest it saves on its own.
Timing is what makes it work. The overpayment has to land before your remortgage valuation, and the lender’s valuer decides which side of the line you fall on, so you need a realistic view of what the property’s worth. Worth a conversation a few months before your deal ends, not a few weeks.
Use the property value field in the calculator to see where an overpayment leaves your LTV, and our remortgage calculator to compare deals once you are below the line.
Reducing the term saves considerably more interest. On £200 a month extra on the example mortgage, shortening the term saves £22,936, while keeping the term and lowering the payment saves about £11,900, roughly half.
| Reduce the term | Reduce the monthly payment | |
|---|---|---|
| What happens | You keep paying the same and finish sooner | Your payment drops, the end date stays put |
| Interest saved | Considerably more | Much less |
| Flexibility | Lower, you are committed to the payment | Higher, useful if money is tight |
| Best for | Anyone whose budget can take it | People who want breathing room now |
Reducing the term is where the saving is. Reducing the payment feels better month to month but hands most of the benefit back. If you’re undecided, some lenders let you overpay ad hoc without formally changing either, which keeps your options open.
Not always. Lenders handle this differently, and some let you choose each time. Santander, for example, lets you choose for a one-off overpayment, but regular overpayments always shorten the term (Santander). Tell your lender which you want when you overpay, then check your next statement.
Most fixed-rate mortgages let you overpay up to 10% a year without an early repayment charge. Go over it and you usually pay an early repayment charge of 1% to 5%, worked out on the amount repaid or the balance depending on the lender. On a large lump sum, that can wipe out years of saved interest in one go.
Lenders measure the 10% differently, and the details are what catch people out:
The allowance is normally worked out on the balance at the start of your mortgage year, and your mortgage year is often the completion anniversary rather than January. Some lenders let you carry unused allowance forward and plenty don’t. Trackers and variable rates frequently have no cap at all.
Your mortgage offer states the exact terms, and if you can’t find it your lender will tell you on the phone. It’s a five minute job that’s much better done before you move the money than after.
Overpaying usually wins when your mortgage rate is higher than the interest you would earn on savings after tax. If your savings interest is taxed, the savings rate has to be well above your mortgage rate to beat overpaying.
| Your tax band | Personal Savings Allowance | Savings rate needed to beat a 4.5% mortgage, once over the allowance |
|---|---|---|
| Basic rate | £1,000 | 5.62% |
| Higher rate | £500 | 7.50% |
| Additional rate | £0 | 8.18% |
Allowances are from GOV.UK. Interest inside the allowance or in a cash ISA is tax free, so there the test is simply savings rate against mortgage rate. Tax rates on savings income are due to rise from April 2027 (GOV.UK), which tilts the sums further towards overpaying.
Beyond savings, there’s a rough order most people work through.
| Option | When it tends to make sense |
|---|---|
| Clear expensive debt first | Credit cards and unsecured loans almost always cost more than your mortgage |
| Build an emergency fund | Money overpaid is hard to get back out. Three to six months of outgoings first |
| Overpay the mortgage | When your mortgage rate beats what you would earn on savings after tax |
| Save or invest instead | When returns beat your mortgage rate, allowing for risk and tax |
| Buy an investment property | Income and gearing, but also work, risk and tax that overpaying does not carry |
| Pension contributions | Tax relief can make these efficient, particularly at higher rate |
| Offset mortgage | When you want overpayment-level savings but need to keep access to the cash |
The simplest test is your mortgage rate against your savings rate after tax. None of this is advice on your own position, and anything involving pensions or investments is worth taking proper advice on.
If the mortgage you’re overpaying is on a rental, the maths changes, and not in the direction most people assume.
Held personally, you no longer deduct mortgage interest as an expense. You get a basic rate tax credit instead, so overpaying reduces your interest and reduces the credit alongside it. For higher rate landlords it usually still comes out positive, but by less than the headline rate suggests. Held in a limited company, interest is still a fully deductible business expense, which makes the effective cost of company borrowing lower than the rate on the paper and overpaying correspondingly less attractive than it looks.
Most buy-to-let is interest only, so overpaying doesn’t shorten a term. What it does is cut the balance, which lowers your monthly interest straight away and improves your LTV for the next remortgage or capital raise.
Which brings up the question portfolio landlords actually wrestle with: is spare cash better used clearing debt on one property, or as a deposit on the next one? Our rental yield calculator will show you what a purchase would need to return to beat what overpaying saves you, and we can stress test the borrowing side. We arrange buy-to-let mortgages every week, from single lets to HMOs, MUFBs and full portfolios.
Six figures and two choices. Here is what each one means.
| Field | What to enter |
|---|---|
| Outstanding balance | What you owe now, not what you originally borrowed |
| Years remaining | The term left to run, on your annual statement |
| Interest rate | Your current rate. If your fix ends soon, try a higher figure too |
| Property value | So we can show what the overpayment does to your LTV |
| Regular overpayment | An amount you can keep up. Consistency beats a one-off |
| Lump sum | Check it against your 10% allowance first |
Then run it again with a smaller overpayment started sooner. Starting earlier usually beats paying more later, and seeing the two side by side makes that obvious in a way a paragraph doesn’t.
Clever Lending is a specialist property finance brokerage, authorised and regulated by the Financial Conduct Authority. Overpaying is between you and your current lender, and you don’t need a broker to do it. Where we’re useful is what comes next.
If you’re overpaying to drop an LTV band before a remortgage, the timing and the valuation both matter and we’ll tell you straight whether it’s worth doing. If your income comes from a limited company, self-employment or several sources, that’s a complex income mortgage and the lender list narrows quickly. And if you’re weighing clearing debt against buying the next property, we’ll run the numbers on both sides rather than just the one that earns us a fee.
Send us the outline and we’ll come back within 24 business hours with a clear route forward. No fees until we’ve found you a solution, and you’ll speak to an advisor from the first call, not a triage team.
You can see everything we arrange on our borrower finance options page.
Overpaying is between you and your current lender. Where we are useful is what comes next: dropping an LTV band before a remortgage, complex income, or weighing clearing debt against buying the next property.
On a £200,000 mortgage at 4.5% with 20 years left, £100 a month extra saves £12,949 and £200 a month saves £22,936. The saving depends on your balance, rate and remaining term, and it is largest when you start early and shorten the term.
Yes, if you can keep it up and have no more expensive debt. £50 a month on a £200,000 mortgage at 4.5% with 20 years left saves £6,923 and clears it 14 months early. Small regular amounts stay well inside the 10% allowance.
Every £200 goes straight off the balance, so you pay less interest from that month on. On a £200,000 mortgage at 4.5% with 20 years left, it saves £22,936 and makes you mortgage free four years early.
On most fixed rates, up to 10% of the balance each year. Above that, expect an early repayment charge, usually 1% to 5%. Trackers and standard variable rates often have no limit. Your mortgage offer gives the exact terms.
On a fixed rate, the practical limit is the penalty-free allowance, usually 10% a year. You can pay more, but the excess usually triggers an early repayment charge. On a variable rate with no charge, you can usually overpay as much as you like, up to the full balance.
Not always. Some lenders recalculate your monthly payment instead, and some ask you to choose each time. Tell your lender you want to shorten the term when you overpay, and check your next statement.
Pay what the mortgage would cost over 20 years. On £200,000 at 4.5%, that means £1,265 a month instead of £1,013, or £252 extra. It saves about £61,100 in interest if the rate stays the same.
Reduce the term if your budget allows. It saves about twice as much interest as lowering the payment. Lowering the payment makes sense when you need breathing room, since the commitment can be hard to undo.
Compare your mortgage rate with your savings rate after tax. If the mortgage rate is higher, overpaying usually wins. Clear more expensive debt first, and keep three to six months of outgoings accessible, because overpaid money is hard to get back.
Yes. Lenders price in loan to value bands, so an overpayment that takes you just below a threshold, such as from 81% to 80%, can move you onto a cheaper rate. Over a five-year fix, that can be worth more than the interest the overpayment saves.
Usually not. Some lenders offer a borrow-back facility, and offset mortgages let you draw on savings that reduce your interest. On a standard mortgage, the money is gone into the debt.
It depends on how you own it. Held personally, you get only a basic rate tax credit on mortgage interest, so overpaying saves a little less than it appears. In a limited company, interest is a deductible expense, which makes overpaying less attractive. Most buy-to-let is interest only, so overpaying cuts the balance and your LTV rather than the term.
Overpaying is a guaranteed return equal to your mortgage rate, with no work attached. A rental generates income and can be geared, but carries voids, maintenance, tax and risk. Our rental yield calculator shows what a property would need to return to beat what overpaying saves you, and we can stress test the borrowing before you commit to anything.
You can, and if you’re carrying expensive unsecured debt it’s often the better move. It does mean securing that debt against your home and usually spreading it over a longer term, so the monthly cost falls while the total often rises. Our second mortgage calculator shows the cost of raising money without touching your existing rate.
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