Fixed versus variable mortgages: how they actually differ

For most households the mortgage is the largest single financial commitment they will make, and the choice between a fixed and a variable rate shapes the monthly cost for years. The decision is often framed as a bet on where interest rates are heading, but that framing can lead you astray.

Fixed rates: certainty for a price

With a fixed-rate mortgage, your interest rate is locked for a set period, commonly two or five years. Your monthly payment stays the same for that term regardless of what happens to the Bank of England base rate or the wider market. That is the appeal: you know exactly what you are paying, which makes budgeting straightforward and protects you if rates rise.

The trade-offs are real. If rates fall during your fixed term, you do not benefit and stay on your higher rate. Fixed deals also usually carry early repayment charges, so leaving or overpaying beyond a set limit before the term ends can be expensive. And when the fix ends, you roll onto the lender’s standard variable rate unless you remortgage, which is usually the moment to act rather than drift.

Variable rates: movement in both directions

Variable-rate mortgages move over time. There are a few kinds. A tracker follows the Bank of England base rate plus a fixed margin, so it moves directly with it. A discount rate is set below the lender’s standard variable rate for a period. The standard variable rate itself is the lender’s own rate, which they can change largely at their discretion, and it is often the most expensive place to sit.

The advantage of a variable rate is that if rates fall, your payments can fall too, and some variable deals have no early repayment charges, giving you flexibility to overpay or leave. The risk is the mirror image of the fix: if rates rise, your payments rise, and you have to be able to afford that.

How to actually choose

The most useful question is not where you think rates are going, because even professionals get that wrong. It is how much movement in your monthly payment your budget could absorb. If a rise of a couple of hundred pounds a month would cause real difficulty, the certainty of a fix has genuine value even if it costs a little more. If you have headroom and value flexibility, a variable rate may suit.

Also weigh the fees. A headline rate with a large arrangement fee can work out dearer than a slightly higher rate with no fee, especially on a smaller loan, so compare the total cost over the deal period, not just the rate. Rates and deals change constantly, so check current products and, if you want a recommendation for your circumstances, speak to a regulated mortgage adviser. MoneyHelper offers free, impartial guidance to start from.