Estimate the impact of a Bank Rate change
Use this tool to estimate how a change in the Bank of England base rate could affect your savings return or interest-only borrowing cost.
Why this calculator matters
The Bank of England base rate influences borrowing and savings costs across the UK economy. When the Monetary Policy Committee raises or lowers rates, banks and lenders may adjust mortgage rates, savings rates, credit products, and business lending.
But the change is rarely identical for everyone. Some lenders pass through most of the rate move. Others pass through only part, and often with a delay. This calculator helps you estimate that real-world impact with a flexible pass-through setting.
How the calculator works
Step 1: Measure the Bank Rate move
The calculator finds the difference between the current and new Bank of England rates.
Step 2: Apply pass-through
That move is multiplied by your pass-through percentage, reflecting how your own account or loan responds.
Step 3: Estimate your new product rate
Your updated rate is calculated as:
- New product rate = Current product rate + (Bank Rate move × pass-through)
Step 4: Project the impact
For savings, the tool shows projected growth using monthly compounding. For borrowing, it gives an interest-only estimate of monthly and total interest cost.
What each input means
- Balance amount: Your savings pot or outstanding loan amount.
- Current and new Bank Rate: The before-and-after policy rates you want to model.
- Pass-through (%): How much of the policy change is reflected in your own rate.
- Current product rate: Your existing savings or loan rate. If left blank, the calculator uses current Bank Rate as a starting point.
- Time horizon: Number of months for projection.
Example scenarios
Savings example
You hold £20,000 in a variable savings account at 4.5%. If Bank Rate rises by 0.25% and your bank passes on 80% of that move, your account rate increases by 0.20%. Over 12 months, that can produce a noticeable increase in interest earned.
Borrowing example
If you have a £150,000 interest-only mortgage and your lender passes through rate cuts quickly, a 0.50% cut in effective rate may reduce monthly interest costs materially. The tool helps estimate that change before you receive official statements.
Important limitations
- This is an estimate, not a lender quote.
- Loan mode assumes interest-only cost for simplicity. Repayment mortgages have principal amortization and may behave differently.
- Real products can include fees, floors, caps, margin rules, and timing delays.
- Savings products may have bonus rates, tiered rates, or withdrawal restrictions.
Practical tips for UK households
- Check whether your mortgage is fixed, tracker, discounted variable, or standard variable rate.
- Review the terms for how quickly rate moves are applied.
- For savings, compare easy-access, notice, and fixed-term products after each Bank Rate decision.
- Run multiple pass-through assumptions (e.g., 50%, 75%, 100%) for scenario planning.
Frequently asked questions
Is this an official Bank of England calculator?
No. This page is an educational estimate tool inspired by how policy rate changes can filter through to consumer products.
Why might my actual rate differ?
Banks use funding costs, competitive strategy, and product design when setting rates. The base rate is important, but it is not the only factor.
Can I use this for mortgages?
Yes, as a quick interest-only approximation. For full repayment mortgage projections, use an amortization calculator with loan term and payment schedule.
Educational use only. Not financial advice.