Compare Mortgages Side by Side
| Deal A | Deal B | |
|---|---|---|
| Borrowing | £255,000 | £255,000 |
| Monthly payment | £1,417 | £1,374 |
| Total interest | £170,212 | £157,291 |
| Fees | £0 | £999 |
| Interest + fees | £170,212 | £158,290 |
| Total repaid | £425,212 | £413,290 |
| Term | 25 years | 25 years |
Deal B is cheapest both monthly and overall.
Put two or three mortgage deals side by side and see which one genuinely costs less — including fees, which is where the cheapest-looking rate often stops being the cheapest deal. Each column has its own price, deposit, rate, term and fees.
How it works
Each deal is amortised separately using the standard repayment formula, then the results are lined up row by row. The monthly payment comes from the first month of the schedule; the total interest is accumulated across every month of the full term.
The row that matters most is interest + fees. That is the true cost of borrowing under each deal — what you hand over beyond the amount you actually borrowed. The tool highlights the lowest monthly payment and the lowest overall cost separately, because they are often two different deals.
Fees are treated as paid upfront rather than added to the loan. If your lender adds the fee to the balance you will pay interest on it too, which makes the gap slightly wider than shown here.
Worked example
Take £255,000 borrowed over 25 years. Deal A is 4.5% with no fee; Deal B is 4.2% with a £999 fee. Deal B has the lower monthly payment — £1,374 against £1,417 — and saves about £12,900 in interest over the full term. Even after the fee that is roughly £11,900 ahead, so paying it is comfortably worth it.
Now borrow £50,000 over 10 years instead. The same 0.3% rate difference is only worth about £864 in interest over that shorter, smaller loan — less than the £999 fee. Deal B still has the lower monthly payment, but Deal A is about £135 cheaper overall. The ranking reverses purely because of the size and length of the loan.
Between those two extremes the gap narrows gradually: at £80,000 over 10 years, Deal B wins by under £400. That is the whole argument for comparing with your own figures rather than picking the lowest rate.
Common questions
Why is the deal with the lowest monthly payment not always the cheapest?
Two things get in the way. A longer term lowers the monthly payment but means far more interest overall, and a low headline rate is often paired with a large arrangement fee. Comparing the interest-plus-fees row rather than the monthly row is what tells you which deal actually costs less.
Should I include the arrangement fee in the comparison?
Yes. A deal at 4.2% with a £999 fee and one at 4.5% with no fee can easily end up within a few hundred pounds of each other, and which wins depends on how much you are borrowing. The fee row exists precisely so that comparison is visible.
How do I compare a two-year fix against a five-year fix?
This tool compares deals over the full term at a constant rate, which is the right way to see the underlying cost. To model what happens when a short fix ends and reverts to a higher rate, use the rate-change option on the main mortgage calculator instead.
Can I compare different property prices or deposits?
Yes — each column has its own price and deposit, so you can compare buying at two different price points, or the effect of putting down a larger deposit on the same property.
Does this account for early repayment charges?
No. Early repayment charges only apply if you leave a deal before it ends, and they vary by lender, so they are not modelled here. Check the offer document if you expect to remortgage or move partway through.
Are these figures a quote?
No. They are estimates based on the numbers you enter, using the standard repayment formula. A lender’s illustration is the only figure that binds anyone, and this is not financial advice.