Compare Two Mortgages
Comparing two mortgage deals side by side sounds simple, but a genuinely important subtlety is easy to miss: the deal that costs less during its own fixed period is not always the deal that costs less over the full mortgage term. This calculator deliberately shows both comparisons separately, since they can point to different answers, and understanding why matters before choosing between two real offers.
Compare Two Mortgages
Compare the true cost of two mortgage deals side by side including fees.
Why the Cheaper Deal Now Isn’t Always the Cheaper Deal Overall
A mortgage with a lower rate but a shorter fixed period can look like the clear winner when you compare just the cost of that fixed period, but a full-term comparison tells a different story once you factor in what happens for the remaining years at the assumed ongoing rate. This calculator runs both comparisons independently — cost over the deal period specifically, and cost over the entire mortgage term — precisely because relying on only one of these can lead to a genuinely different, and sometimes worse, decision than looking at both together.
This is worth checking specifically whenever an upfront fee is involved, since a fee has an outsized effect on a short comparison window but becomes proportionally smaller the longer the mortgage runs — exactly the mechanism behind why a fee-heavy deal can lose the short comparison while still winning the long one.
Two Deals, Two Different Winners
A £220,000 mortgage over 25 years compared between a 3.9% rate with a £1,999 fee and a 4.3% rate with no fee, both on a 2-year deal, shows the higher-rate, fee-free option winning the deal-period comparison by roughly £826 — the upfront fee outweighs the modest rate saving over just two years. But run the same two rates across the full 25-year term, and the lower-rate option wins by roughly £12,660 instead, since the monthly saving keeps compounding long after the fee has been left behind. The two comparisons genuinely point to different mortgages here, which is exactly the kind of result worth seeing clearly rather than only checking one of the two.
The Fee-for-Rate Trade That’s Easy to Get Wrong
A mortgage with a meaningfully lower rate but a larger upfront fee is not automatically the better deal, and a fee-free option at a slightly higher rate is not automatically the worse one — which genuinely wins depends on the loan size and how long you intend to keep that specific deal. On a smaller mortgage balance, a large fee can outweigh a modest rate saving fairly quickly, while on a larger balance the same fee is proportionally smaller and easier for the rate saving to overcome. This calculator includes the fee directly in both totals specifically so this trade-off is reflected in the actual pounds compared, not just the headline rate.
A useful rule of thumb worth checking against your own numbers here: divide the fee difference between two deals by the monthly payment difference to get a rough break-even point in months — if you expect to keep the deal well beyond that point, the lower-rate, higher-fee option is more likely to come out ahead; if not, the fee-free option is worth weighing more heavily.
Comparing a Fix Against an Interest-Only Deal Isn’t a Fair Fight
If one mortgage is a standard repayment deal and the other is interest-only, comparing their monthly payments alone is genuinely misleading, since the interest-only option will always show a lower monthly figure without ever reducing the balance owed. This calculator lets you set the repayment type independently for each mortgage specifically so this difference is reflected properly in the full-term total, rather than comparing two numbers that are not measuring the same underlying commitment. The full-term total for an interest-only deal correctly includes the entire original balance still due at the end, alongside the interest paid throughout, giving a genuinely comparable total cost figure against a repayment mortgage that clears the balance progressively instead. If you are specifically comparing your current deal against breaking it early for a better rate, our Ditch Your Fix Calculator is built around exactly that break-even decision, factoring in any early repayment charge.
What to Do With the Two Different Winners
When the deal-period winner and the full-term winner genuinely disagree, the right choice depends on how confident you are about your plans beyond the initial deal — if you expect to remortgage again as soon as the fixed period ends regardless, the deal-period comparison is the more relevant one for your actual situation, while if you expect to let the mortgage run its full course without further action, the full-term comparison matters more. Neither comparison is universally the “correct” one to prioritise; it depends on your own realistic plans for the mortgage, which is precisely why this calculator shows both rather than picking one for you. Our Mortgage Calculator is useful for working through either single option in more depth, including its LTV band, before bringing the two together here for a direct comparison.
Frequently Asked Questions
Should I always pick the deal with the lower headline rate?
Not automatically — the headline rate alone ignores fees and the length of the deal period, both of which can change which option is genuinely cheaper once the full numbers are compared.
What happens after a fixed deal period ends?
Without proactively remortgaging or switching to a new deal, most mortgages revert to the lender’s standard variable rate, which is typically higher than fixed deal rates, so it is worth planning ahead of the deal ending rather than allowing an automatic reversion.
Does a longer fixed period always cost more overall?
Not necessarily — a longer fix provides more certainty and protection against future rate rises, and while longer fixes often carry a slightly higher rate than shorter ones, this is a trade-off between certainty and cost rather than a straightforward rule that longer always costs more.
Should I include arrangement fees added to the loan rather than paid upfront?
Yes — whether a fee is paid upfront or added to the mortgage balance, it represents a real cost either way, and leaving it out of the comparison would understate the true cost of whichever deal includes it.
Is it worth comparing more than two deals at once?
This calculator is built for a direct two-way comparison, but running it multiple times with different deal combinations is a practical way to compare several real offers against each other before making a final decision.
Important Information
This calculator provides an estimate based on the figures you enter and does not constitute financial advice. Actual mortgage costs depend on full lender terms and conditions. For advice specific to your circumstances, consult a mortgage broker or FCA-regulated adviser. See our Disclaimer for further information.