Compare two UK mortgage deals side by side — not just on the headline interest rate, but on what each one actually costs you. Enter the loan amount once, then fill in the rate, initial fixed period, full term, product fee and repayment type for Deal A and Deal B. The calculator works out the monthly payment and total cost over each deal's initial period, including fees, and tells you which deal is genuinely cheaper and by how much.
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You are comparing two mortgage deals on the same loan amount. Each deal has its own interest rate, initial fixed period, full mortgage term, product fee and repayment type, so the fairest way to compare them is on total cost over the initial period — not the headline rate alone.
Based on the figures you entered, the calculator works out the monthly payment for each deal, the total amount paid over its initial fixed period (monthly payments plus the product fee), the balance remaining at the end of that period, and an effective "true cost per year" figure for comparison.
Your calculation summary shows the totals for Deal A and Deal B over their initial fixed periods, and identifies which deal costs less overall.
This calculator gives an estimate for comparison purposes only, based on the figures you enter. It does not constitute financial advice. Always check the lender's official Key Facts Illustration (KFI) or European Standardised Information Sheet (ESIS) and speak to a qualified mortgage adviser before choosing a deal.
This tool compares two mortgage deals on exactly the same loan amount, so the only variables are the ones that actually differ between offers: the interest rate, how long that rate is fixed or discounted for, the overall mortgage term, the product (arrangement) fee, and whether you're repaying capital and interest or interest only. It then works out the monthly payment, the total amount you'd pay over each deal's initial period including the fee, how much balance would be left at the end of that period, and which deal is cheaper overall.
It's designed for comparing two specific offers you've already been quoted — for example two deals from a broker, or a deal from your current lender against a competitor — rather than for working out whether you can afford a mortgage in the first place.
The single biggest mistake people make when comparing mortgages is looking only at the interest rate. Two deals with the same rate can cost very different amounts once you factor in the fee, and two deals with different rates can cost almost the same once the fee is included. The only reliable comparison is total cost over a common time horizon — normally the initial fixed or discounted period, since that's the period you can actually be confident you'll be on that deal for.
To compare properly: take the monthly payment for each deal, multiply it by the number of months in the initial period, then add the product fee. Whichever number is lower is the cheaper deal over that period — regardless of which one has the "better" headline rate. This calculator does that arithmetic for you automatically.
Product (or arrangement) fees on UK mortgages typically range from £0 on fee-free deals up to £1,500–£2,000+ on some of the lowest-rate deals, which are often priced that way deliberately — lenders use a lower headline rate plus a higher fee to look more attractive in rate-sorted comparison tables. On a large loan over a long fixed period, the rate saving from a fee-paying deal can easily outweigh the fee. But on a smaller loan, or a short fixed period, the fee can dominate the comparison and make the "cheaper-looking" deal more expensive overall.
As a rule of thumb: the bigger the loan and the longer the fixed period, the more a fee-paying low-rate deal tends to make sense; the smaller the loan and the shorter the fixed period, the more a no-fee or low-fee deal tends to win, even at a somewhat higher rate. There's no shortcut around actually doing the sum for your own numbers, which is exactly what this calculator is for.
A fixed-rate mortgage keeps your interest rate — and therefore your monthly payment, if repaying capital and interest — exactly the same for an agreed period, usually 2, 3, 5 or 10 years, no matter what happens to interest rates generally. You get certainty, but you may pay more than a tracker would have cost if rates fall, and you'll usually face an early repayment charge if you leave before the period ends.
A tracker mortgage charges a rate that moves automatically with a reference rate — almost always the Bank of England base rate — plus a fixed margin set by the lender (for example, "base rate + 0.75%"). Your payments rise and fall as the base rate changes, with no cap unless the deal specifically includes one.
The standard variable rate (SVR) is each lender's own default rate, which they can raise or lower at their own discretion, broadly (but not strictly) in line with the base rate. SVRs are typically several percentage points above the rates on offer for new fixed or tracker deals, which is why almost nobody chooses to stay on one deliberately — it's what you land on if you don't arrange a new deal before your current one ends.
APRC (Annual Percentage Rate of Charge) is a single standardised figure that UK lenders are required to quote, intended to let you compare the total cost of different mortgage products on a like-for-like basis. It combines the initial rate, all fees, and the rate you'd pay after the initial period ends (assumed to be the lender's current SVR), spread evenly across the full mortgage term.
APRC is a useful sanity check, but it has a real limitation: it assumes you stay on the lender's SVR for the entire remaining term after your initial deal ends — something almost no borrower actually does, since most people remortgage onto a new deal instead. This means APRC can understate how attractive a short, cheap fixed deal really is (because it penalises it with years of assumed SVR), and can make a long fixed deal look relatively better than it will actually turn out to be if rates fall and you remortgage early. Comparing actual total cost over the initial period — as this calculator does — is usually more useful for deciding between two specific live offers.
Shorter fixed periods (2 years) usually come with lower rates than longer ones, because the lender is taking on less interest-rate risk. They give you the flexibility to reassess and remortgage sooner if rates fall, but they also expose you to remortgaging costs and rate uncertainty more often, and a fixed product fee is spread over fewer months, making its effective annual cost higher.
Longer fixed periods (5 or 10 years) typically carry a slightly higher rate in exchange for payment certainty over more years, and they spread a fixed fee over more months, reducing its annual impact. The trade-off is reduced flexibility: if rates fall significantly, or your circumstances change and you need to move or remortgage, you may face an early repayment charge to get out of the deal early.
Most fixed and discounted-rate mortgage deals carry an early repayment charge if you pay off some or all of the balance — including by remortgaging to another lender — before the deal ends. ERCs are usually expressed as a percentage of the amount repaid early and commonly taper down each year of the deal, for example 5% in year one, 4% in year two, and so on, reaching 0% once the deal ends.
If you're thinking about switching deals before your current fixed period finishes, always check your existing mortgage offer or annual statement for the exact ERC that would apply, and include it in your comparison — a cheaper new deal can easily be wiped out by a large ERC on your current one.
If you do nothing when your fixed or discounted period ends, your mortgage automatically moves onto your lender's standard variable rate (SVR). Because the SVR is usually significantly higher than the rates available on new deals, and can change at the lender's discretion, most borrowers arrange a new deal — either staying with their existing lender (a "product transfer") or remortgaging to a new one — to take effect from the day their current deal ends, to avoid any time spent on the SVR.
Many lenders let you lock in a new deal several months in advance of your current one expiring, often without an early repayment charge, which is worth doing well before the end date rather than waiting until the last minute.
The "right" fixed period and fee structure depends heavily on how likely you are to stay in the deal for its full length. If you expect to move house, come into money, or want flexibility to overpay significantly within the next couple of years, a shorter fixed period with a lower (or no) fee reduces the risk of paying for rate certainty — or a fee — you don't end up using, and makes a future remortgage cheaper to arrange. If you're settled and want payment stability for longer, a longer fixed period, potentially with a fee if the rate saving justifies it, can make more sense.
Also consider porting: many mortgages can be transferred ("ported") to a new property if you move house during the fixed period, which can avoid an ERC — but porting isn't guaranteed and is subject to the lender re-approving you and the new property, so it shouldn't be assumed as a certainty when planning.
Make sure you're comparing deals on the same repayment basis. A capital-and-interest deal and an interest-only deal on the same loan, rate and term will have very different monthly payments — interest-only is always lower month-to-month because none of the payment reduces the balance — but interest-only leaves the full loan amount outstanding at the end of the term, requiring a separate repayment vehicle (savings, investments, or sale of the property). Comparing an interest-only quote against a capital-and-interest quote purely on monthly payment, without accounting for this, is comparing two different products, not two prices for the same thing.
Say you're comparing two deals on a £200,000 repayment mortgage over a 25-year term, each with a 2-year initial fixed period. Deal A offers 4.5% with a £999 product fee; Deal B offers 4.8% with no fee.
Deal A's monthly payment works out to roughly £1,112, so over 24 months that's about £26,680 in payments, plus the £999 fee — a total of around £27,679 over the initial period. Deal B's monthly payment is roughly £1,146, so over 24 months that's about £27,504 in payments, plus no fee — a total of around £27,504. Despite its higher rate, Deal B is cheaper here by around £175 over the two-year period, because the gap in monthly payments (about £34/month) doesn't add up to more than the £999 fee over just 24 months. Stretch the comparison to a 5-year fixed period instead, and the result could easily flip, since the rate saving would have longer to compound against the fixed fee.
For official, regulator-backed guidance on mortgage disclosure and comparing deals, see the sources below rather than relying on calculators alone: