The honest answer starts with a forecast nobody can make
So this calculator turns the question round. Instead of asking what rates will do, it asks what they would have to do for each choice to win. That number — the break-even rate — is something you can actually hold an opinion about.
The price of the two options in September 2026
The average two-year fix was 5.84% and the average five-year 5.88%. Best-buy, the two-year was 4.66% and the five-year 4.70%, both from Danske Bank, both up to 85% loan to value, both with a £1,124 fee. On £200,000 over 20 years the difference between 4.66% and 4.70% is four pounds a month. Five years of certainty for four pounds a month is an unusual price. It has not always been this cheap and it will not stay this cheap.
What the curve is telling you
For most of 2023 to 2025 five-year fixes were cheaper than two-year ones. That happens when the market expects rates to fall. In September 2026 the five-year fix was dearer than the two-year. The market has stopped pricing in cuts. That is information, not a prediction — the swap market has been wrong before, and in 2026 it was wrong in both directions inside six months.
The rule that changes the answer, if you are moving lender
FCA rule MCOB 11.6.18R requires a lender to assess affordability against likely future rates for at least five years, with a floor of a one percentage point increase. There are two exemptions, and the second one matters: where the rate is fixed for the initial five years or more, no stress test is required at all.
Same borrower. Same income. Take a two-year fix and you are assessed on the rate plus at least one point. Take a five-year fix and you are assessed on the rate you will actually pay. A longer fix can let you borrow more. Ask the broker directly: "Does a five-year fix change the maximum you can lend me?" The answer is often yes and the question is rarely asked.
It does not matter on a straight product transfer, because a product transfer with no additional borrowing needs no affordability assessment at all. There is no stress test to escape because there is no test.
Before you use this
This is general information, not financial advice. It does the math on the numbers you type in. It does not know your circumstances, and it does not recommend any lender, product or course of action. Nothing you type here is stored or sent anywhere. It stays on your phone and disappears when you close the page. There is no account, no sign-up and nothing saved.
