Fixed vs Variable Rate Mortgage: Which Costs Less?

How each rate type works

Fixed rate: Your interest rate stays the same for an agreed period — typically 2 or 5 years in the UK, or 15 to 30 years in the US. If you fix at 4.5%, you pay 4.5% regardless of what happens to central bank rates. When the fix ends (in the UK), you move to the lender’s standard variable rate unless you remortgage.

Variable rate: Your rate moves with the market. In the UK, this means a tracker (Bank of England base rate + a set margin) or a standard variable rate (SVR) set by the lender. In the US, adjustable-rate mortgages (ARMs) typically fix for 5 or 7 years, then adjust annually based on an index like SOFR.

The maths: when does fixed save money?

Take a £250,000 mortgage over 25 years. In early 2025-26, a typical 5-year fix sits around 4.5% while a 2-year tracker starts at 4.0%.

Fixed at 4.5%: Monthly payment of £1,390. Over 5 years, you pay £83,400 in total payments and owe £213,800 remaining.

Tracker at 4.0% initially: Monthly payment starts at £1,320 — £70/month cheaper. But if the Bank of England raises rates by 0.5% in year 2 and another 0.5% in year 3, your rate hits 5.0% and your payment jumps to £1,461.

The break-even point: if rates rise by more than about 0.5% on average over your mortgage term, the fixed rate saves money. If rates stay flat or fall, the variable rate wins.

The 2025-26 rate environment

Central banks in the US and UK raised rates aggressively in 2022-2024 to fight inflation. As of early 2026, the Bank of England base rate sits at 4.5% and the US Federal Funds rate at 4.25-4.50%.

Markets are pricing in gradual cuts over the next 2-3 years. If those cuts materialise, variable-rate borrowers benefit automatically. Fixed-rate borrowers stay locked at today’s rates and miss the reduction — though they can remortgage when their fix ends.

This creates an unusual situation: short-term fixes (2 years) let you lock in current rates while giving you the option to remortgage at lower rates relatively soon. Long fixes (5+ years) protect you if rate cuts don’t happen or reverse.

Break-even analysis: how to calculate yours

To determine your break-even point:

1. Find the difference between your fixed rate and variable rate (e.g., 4.5% fixed vs 4.0% variable = 0.5% gap)
2. Calculate how much rates would need to rise before the variable rate exceeds the fixed rate — in this case, any rise above 0.5%
3. Estimate how long rates need to stay elevated to wipe out the early savings from the lower variable rate

Use a mortgage payment calculator to model 3 scenarios: rates stay flat, rates rise 1%, and rates fall 1%. Compare total interest paid across the full term. The scenario where the difference is smallest tells you this decision matters less than you think — and the one where it’s largest tells you how much you’re gambling.

When to choose fixed

• You’re stretching to afford the mortgage and can’t absorb a payment increase
• You’re on a tight budget with little room for surprise expenses
• Rates are historically low and more likely to rise than fall
• You value predictability and sleep better knowing your payment won’t change
• You’re buying in the US and can lock for 30 years (this is unusual globally — most countries don’t offer fixes beyond 5-10 years)

When to choose variable

• You can afford payments even if rates rise 2-3%
• Rate cuts are widely expected and you want to benefit immediately
• You plan to sell or remortgage within 2-3 years (avoiding early repayment charges on a fix)
• You want flexibility to make unlimited overpayments
• The gap between fixed and variable is large (1%+), making the fixed premium expensive

The UK remortgage cycle

Most UK borrowers remortgage every 2-5 years when their fix ends. This means the fixed vs variable decision isn’t permanent — it’s a 2-5 year bet on rate direction. Start comparing deals 3-6 months before your fix expires. Falling onto your lender’s SVR (often 7-8%) costs hundreds per month.

Set a reminder in your calendar when your fix ends. Missing the remortgage window is one of the most expensive financial mistakes UK homeowners make.