TL;DR - What Are Swap Rates?
- Swap rates are wholesale interest rates set in financial markets that lenders use to price fixed-rate mortgages - when swap rates rise, fixed mortgage rates follow, often within days
- A 2-year swap rate underpins 2-year fixed mortgages; a 5-year swap rate underpins 5-year fixed mortgages - lenders add a margin on top to cover costs and profit
- Swap rates move independently of the Bank of England base rate - they are set by bond markets and reflect expectations about where interest rates will be over the fixed term
- When markets expect rates to fall, longer-term swap rates drop below shorter-term rates - creating what is called an inverted yield curve, where 5-year fixes become cheaper than 2-year fixes
- You cannot access swap rates directly as a borrower - they are interbank rates. Your mortgage rate is the swap rate plus the lender's margin (typically 0.5% to 1.5%)
- Monitoring swap rates gives borrowers early warning of where mortgage rates are heading before lenders make announcements
Last reviewed: June 2026 - Sources: Bank of England, ICE Benchmark Administration
KEY FACTS - SWAP RATES UK 2026 | |
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Swap rates are the interest rates at which large financial institutions lend to each other in the interbank market for a fixed period. In the UK mortgage market, the relevant rates are SONIA-based interest rate swaps - typically the 2-year and 5-year rates. These rates determine what it costs a mortgage lender to lock in funding for the term of a fixed-rate mortgage, and therefore set the floor for the rates lenders can offer to borrowers.
How Swap Rates Work
When a lender offers you a 5-year fixed mortgage at 4.5%, it needs to fund that lending at a known cost for 5 years. To do this, it enters an interest rate swap in wholesale financial markets - effectively locking in a fixed funding rate for the 5-year period. The cost of that swap is the 5-year swap rate. The lender then adds its margin - covering operating costs, credit risk, and profit - on top.
So if the 5-year swap rate is 3.8% and the lender adds a 0.7% margin, the resulting mortgage rate is 4.5%. If swap rates rise to 4.2%, the same lender would need to charge at least 4.9% to maintain the same margin - which is why lenders reprice their fixed rate products when swap rates move significantly.
Swap Rates vs Bank of England Base Rate
| Rate | Set By | Affects | Frequency |
|---|---|---|---|
| Bank of England base rate | Monetary Policy Committee (8 times per year) | Variable rate mortgages, tracker mortgages, savings rates | 8 scheduled decisions per year |
| Swap rates (2yr, 5yr) | Financial markets, gilt yields, global rate expectations | Fixed rate mortgages | Continuously, intraday |
The base rate and swap rates often move in the same direction over time, but not in lockstep. In 2023-24, swap rates fell before the Bank of England cut the base rate - meaning fixed mortgage rates started falling months before the official rate cut. Borrowers who understood swap rates were able to anticipate the mortgage market move.
The Yield Curve and Fixed Mortgage Pricing
Normally, longer-term swap rates are higher than shorter-term rates - reflecting the greater uncertainty of committing to a rate further into the future. This means 5-year fixed mortgages are usually priced higher than 2-year fixed mortgages.
When markets expect interest rates to fall significantly, this relationship can invert. The 5-year swap rate falls below the 2-year swap rate because markets are pricing in lower rates for the medium term. This is called an inverted yield curve, and it produces the unusual situation where 5-year fixes become cheaper than 2-year fixes - as was seen in parts of 2024 and 2025 in the UK.
What Swap Rate Movements Mean for Borrowers
- Swap rates rising: lenders will reprice fixed rate mortgages upward within days - if you are close to needing a mortgage, this is a signal to act quickly or lock in a rate
- Swap rates falling: lenders will cut fixed rates - borrowers with rate applications in progress may benefit from waiting a few days for repricing
- Swap rates stable: mortgage rates stable - no urgency either way on timing
Most mortgage brokers monitor swap rates daily. Borrowers approaching the end of a fixed term can also monitor the Bank of England's published gilt yields and financial data at bankofengland.co.uk as a proxy for swap rate direction.
Tracker Mortgages vs Fixed Rate Mortgages
Tracker mortgages follow the Bank of England base rate directly - they do not use swap rates. A tracker mortgage at base rate + 0.5% will move up or down on the same day the MPC changes the base rate. This makes trackers straightforward to understand but exposes borrowers to base rate increases.
Fixed rate mortgages are priced from swap rates and provide payment certainty for the fixed term regardless of what happens to the base rate or swap rates during that period. Once a fixed rate is agreed and the mortgage is completed, the rate does not change until the fixed term ends.
Disclaimer: Kaeltripton.com is an independent editorial publisher. This guide is factual information only and does not constitute financial advice. Consult an FCA-authorised mortgage broker for advice on mortgage timing and product selection.
What are swap rates?
Swap rates are wholesale interbank interest rates that mortgage lenders use to price fixed-rate mortgages. The 2-year and 5-year SONIA swap rates in the UK determine the cost of fixed-rate mortgage funding. Lenders add a margin on top to set the mortgage rate offered to borrowers.
Why do mortgage rates change when swap rates change?
Lenders fund fixed-rate mortgages by entering interest rate swaps in wholesale markets. If swap rates rise, the cost of funding increases and lenders must raise mortgage rates to maintain their margins. Repricing typically happens within 1 to 5 days of a significant swap rate move.
Are swap rates the same as the Bank of England base rate?
No. The base rate is set by the Monetary Policy Committee 8 times a year and directly affects variable rate and tracker mortgages. Swap rates are set continuously by financial markets and affect fixed rate mortgages. They often move in the same direction over time but are independent of each other.
How can I monitor swap rates?
The Bank of England publishes gilt yields at bankofengland.co.uk which track closely with swap rates. Financial data providers including Bloomberg and ICE Benchmark Administration publish SONIA swap rates. Most mortgage brokers monitor these rates daily and can advise on timing.
Sources: Bank of England base rate and monetary policy decisions (bankofengland.co.uk); ICE Benchmark Administration SONIA data; FCA Mortgage Conduct of Business sourcebook (MCOB); UK Debt Management Office gilt yield data (dmo.gov.uk).
