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Mortgage Comparison Calculator — Compare Two Deals

A lower rate does not always mean a cheaper mortgage once fees are counted. Enter two deals — rate, initial period, rate afterwards, fees and cashback — and see monthly payments, the interest and fees you will pay, and which deal is cheaper over the period you choose.

How to use the Mortgage Comparison Calculator

  1. Enter the amount you want to borrow and the mortgage term.
  2. Choose how long to compare the cost over, such as the initial deal period.
  3. Fill in both deals: rate, initial period, follow-on rate, fees and cashback.
  4. See which deal is cheaper, with monthly payments and a cost chart.

Rate versus fees

A mortgage with a lower rate but a high product fee can cost more than a slightly higher rate with no fee, especially on smaller loans or short deal periods. Comparing the true cost — interest plus fees, less any cashback — over the same period shows which deal really wins.

If a fee is added to the loan, you pay interest on it for the whole term, so adding fees to the mortgage usually costs more than paying them upfront.

What happens after the initial period

Most fixed and discounted deals last two to five years, after which you move to the lender’s standard variable rate unless you remortgage. The calculator lets you enter a rate for after the initial period so you can see the payment jump and the cost over longer horizons.

Because the true future rate is unknown, the long-term figures are indicative only. Many borrowers remortgage at the end of the deal, so the cost over the initial period is usually the most useful comparison.

Assumptions & important information

  • Payments are calculated monthly with the interest rate for each period applied to the outstanding balance.
  • At the end of the initial period the payment is recalculated at the follow-on rate over the remaining term; the follow-on rate is an assumption that you choose.
  • True cost is the interest paid plus fees, less cashback, over the period selected. Capital repaid is not a cost.
  • Early repayment charges, valuation and legal fees (unless you enter them) and rate changes during the initial period are not included.
  • Interest rates shown in the form are examples only, not current market rates. Enter the rates from your own quote.
  • This calculator gives estimates for information only. It is not financial advice and not a mortgage or loan offer. Rates, fees and lender criteria vary, so check the details with your lender or a regulated adviser. Your home may be repossessed if you do not keep up repayments on a mortgage or other debt secured on it.

Ideas & examples

  • Lower rate with a fee vs higher rate with no fee: On £250,000 over 25 years, a 4.2% deal with a £999 fee costs £1,347.36 a month; a 4.6% deal with no fee costs £1,403.81. Over 5 years the true cost is £50,364 versus £54,241.
  • Cashback deals: Add the cashback amount to see how a deal with a higher rate and cashback compares with a lower-rate deal without it.
  • Comparing over the full term: Choose “The full mortgage term” to see how much each deal would cost if you stayed on it, with the follow-on rate applying after the initial period.

Frequently asked questions

How do I compare two mortgage deals?

Compare the true cost over the same period: interest paid plus fees, less any cashback. This calculator does that automatically alongside the monthly payments.

Should I choose a lower rate or lower fees?

It depends on the loan size and deal length. A lower rate saves more on larger loans and longer deals, while no-fee deals can win on smaller loans or short deals. The calculator shows the exact difference.

What happens when my initial deal ends?

You usually move to the lender’s standard variable rate, which is often higher. Many borrowers remortgage before this happens.

Is it better to add the fee to the loan?

Adding the fee to the loan avoids paying upfront but you pay interest on it for the term, so it costs more overall. Tick the box in the calculator to see the effect.

Does the calculator include legal and valuation fees?

Add them to the “Product & booking fees” box if they differ between the two deals. Free legal work and free valuations can be entered as zero.

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