Remortgage calculator
A remortgage calculator compares your current mortgage against a new deal and shows the saving. On a £200,000 balance over 20 years, moving from 5.5% to a new 4.2% deal cuts the monthly payment by about £143 and saves roughly £7,500 over a 5-year deal after a £999 fee. This free tool shows your own monthly saving and the saving over the deal, net of the fee. It runs in your browser, needs no email, and stores nothing.
Compare your current deal with a new one
Free. No email needed. Runs in your browser, stores nothing.
Current monthly
£1,376
New monthly
£1,233
Saving over the deal
£7,559
Worked example: on a £200,000 balance over 20 years, moving from 5.5% to 4.2% cuts the monthly payment by about £143. Over a 5-year deal that is about £8,558, or £7,559 after the £999 fee. Change the figures above for your own case.
Simplified illustration for a repayment mortgage, with each rate assumed held for the whole term. It ignores valuation and legal costs, any early repayment charge on your current deal, and future rate changes. Not a quote and not advice. A regulated broker can confirm the real total cost.
How to read the result
The monthly saving is the immediate difference in your payment. The saving over the deal spreads that across the length of the new fixed or discounted period and takes off the product fee, which is the fairer way to compare deals. A low rate with a big fee can beat, or lose to, a higher rate with no fee, and only the total tells you which. If you are still inside your current deal, check the early repayment charge too, because that can wipe out an early switch.
Switch, or stay with your lender?
Remortgaging to a new lender opens the whole market but needs a fresh affordability check. A product transfer keeps you with your current lender, usually with little re-underwriting, which can be the safer route if your income has changed. Weigh them with the switch or stay tool and read remortgage vs product transfer.
Common questions
How does this remortgage calculator work?
It works out your current monthly payment from your balance, rate and remaining term, then does the same at the new rate. The difference is your monthly saving. It then multiplies that saving across the length of the new deal and subtracts the product fee, to show the saving net of the fee over the deal period. Both figures assume a repayment mortgage at a rate held for the whole term.
Should I add the product fee to the loan or pay it up front?
Paying a fee up front avoids paying interest on it, but adding it to the loan keeps your cash free. This tool subtracts the fee from your saving so you see the true net benefit either way. If you add it to the loan, remember you then pay interest on it for the term, which a broker can factor in precisely.
Is the cheapest rate always the best remortgage?
No. A lower rate with a high fee can cost more overall than a slightly higher rate with no fee, especially on a smaller balance where the fee is a bigger share. Always compare the total cost over the deal, including the fee, not just the headline rate. That is exactly what this calculator and a good broker do.
Do I need to remortgage, or can I stay with my lender?
You can often stay with your current lender and take a new rate, called a product transfer, usually with little or no re-underwriting. A remortgage moves you to a new lender with a full affordability check but can access the wider market. Our switch or stay tool and the remortgage vs product transfer guide compare the two.
Worried about the jump when your fix ends? Try the payment-shock calculator, and see when your fixed rate ends.
Founder, MortgageExplained, MortgageExplained
Adam spent nearly a decade as a mortgage adviser at Just Mortgages, with further experience in commercial finance. He is CeMAP and CF qualified. He built MortgageExplained to do one thing well: explain mortgages in plain English, then introduce you to a regulated broker when you are ready. Every page is written and reviewed by Adam.
Last reviewed: 21 July 2026