See how your monthly payment will change at your next rate change, based on the Bank of England base rate and your margin.
Important: This is a guide figure. Your exact new payment depends on the rate your lender applies on the day your deal changes and on your remaining balance at that point.
Understand each figure you need to model your next mortgage rate change
The amount of your mortgage you have not yet repaid. You will find it on your latest mortgage statement or in your lender's online banking under the loan details.
The base rate set by the Bank of England's Monetary Policy Committee is the benchmark that tracker mortgages and most standard variable rates (SVRs) move with. It is reviewed roughly every six weeks.
On a tracker mortgage this is the fixed percentage added to the base rate. It is set out in your mortgage offer and does not change for the life of the tracker deal, even though the base rate does.
The number of years left until your mortgage is fully repaid. Together with the outstanding balance and the new rate, it sets your new monthly payment.
If you expect rates to climb, ask your lender about a product transfer to a fixed deal. Many lenders offer competitive rates to keep you rather than lose you to a remortgage.
The moment your rate is reviewed is a good time to make an overpayment, as it reduces the balance the new payment is calculated on. Most deals allow up to 10% a year penalty-free.
If your lender will not offer a better rate, you can remortgage to another lender. A broker can compare the whole market and many remortgage deals come with free valuation and legal fees.
A mortgage rate review is the point at which the interest rate on your mortgage changes, and with it your monthly payment. On a tracker mortgage this happens whenever the Bank of England changes its base rate; on a standard variable rate (SVR) it happens when your lender decides to move its own rate; and at the end of a fixed-rate deal you revert to the lender's SVR, which is usually a sharp jump.
If you are on a variable or tracker rate, your payment is not fixed: it is recalculated against the new rate and your remaining balance. This calculator helps you anticipate how your monthly payment will change at the next rate change, so you can plan ahead or decide whether to switch deal.
The Bank of England base rate has been on a rollercoaster in recent years: from an emergency low of 0.10% during the pandemic, up to a 16-year high of 5.25% in 2023 as the Bank fought inflation, and gradually back down since. You can read about its history and method on Wikipedia: official bank rate. The Bank of England publishes the official rate after each Monetary Policy Committee meeting.
Figures for December 2025 and June 2026 are illustrative; always check the latest official rate on the Bank of England website.
Let's see how a fall in the base rate affects a typical UK tracker mortgage. With an outstanding balance of £150,000, 20 years left and a margin of +0.75%:
Outstanding balance
£150,000
Remaining term
20 years
Margin
+0.75%
Old rate (4.75%+0.75%)
5.50% → £1,032/month
New rate (4.00%+0.75%)
4.75% → £969/month
Monthly saving
-£63/month
Yearly saving
-£756/year
Outstanding balance
£200,000
Remaining term
22 years
Move
Fix → SVR
Old fixed rate
2.40% → £1,003/month
New SVR
7.25% → £1,512/month
Monthly increase
+£509/month
Yearly increase
+£6,108/year
Reverting to the SVR is usually the costliest outcome — remortgaging before your deal ends often avoids it.
How and when your rate changes depends on the type of deal you are on. The three most common in the UK are:
Upside: your payment is locked for the deal period (typically 2 or 5 years).
Watch out: when the deal ends you revert to the SVR — usually a sharp jump.
Upside: follows the base rate exactly, so you benefit straight away when it falls.
Watch out: your payment also rises immediately when the base rate goes up.
Upside: no early repayment charges, so you can switch or overpay freely.
Watch out: the lender sets it, so it is usually the most expensive option.
To use this calculator you need a few figures from your mortgage. Here is where to find them:
If the uncertainty of a variable rate worries you, there are ways to protect yourself from future increases:
A product transfer with your lender, or a remortgage to a new one, fixes your payment for 2 or 5 years. It is usually a little higher than the best tracker but gives certainty.
Most lenders let you secure a new rate up to six months before your current deal ends, so you can avoid dropping onto the SVR even for a single month.
If you have savings, overpaying (usually up to 10% a year penalty-free) cuts your balance and softens the impact of any future rate rise.
To know the exact rate that will apply when your deal changes, check the official page of the Bank of England — the official bank rate. It is the benchmark lenders use to set tracker and standard variable rates.
Note: This is a guide figure. Your exact new payment depends on the rate your lender applies, your remaining balance on the day the rate changes and the specific terms of your mortgage. This calculator is for information only and is not financial advice.
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We answer the most common questions about variable and tracker mortgage rate changes