Calculate the maturity value and interest earned on a fixed rate savings bond, compounded monthly.
Monthly compounding (example)
A fixed rate bond calculator works out the maturity value and total interest earned on a fixed rate savings bond — a savings account where you deposit a lump sum for a fixed term at a fixed interest rate (AER), with interest compounded monthly until the bond matures. This calculator helps you see exactly how much your deposit will grow to by the end of the term.
This calculator compounds your deposit monthly at a constant rate for the full term — there are no further deposits or withdrawals, reflecting how most fixed rate bonds work (your money is locked away until maturity).
Formula: Each month: Balance = Balance × (1 + monthly rate), where monthly rate = AER ÷ 12 ÷ 100. Maturity Value = Balance after the final month. Total Interest = Maturity Value − Deposit Amount.
Example: A £10,000 deposit at a 4.5% AER (example rate — enter the rate offered by your bond provider) over a 12-month term grows to roughly £10,460 at maturity, meaning about £460 in interest earned. (Note: all figures in this example are for illustration purposes only and do not represent any specific bond offer.)
Fixed rate bonds are a type of savings account offered by UK banks and building societies that pay a guaranteed interest rate (AER — Annual Equivalent Rate, which assumes interest is compounded and reinvested) in exchange for locking your money away for a fixed term, typically from six months to five years. Unlike easy access savings accounts, most fixed rate bonds don't allow withdrawals during the term — or charge a significant penalty (such as loss of interest) if you do — so it's important to only deposit money you won't need before the bond matures. Savings held in UK banks and building societies are typically protected by the Financial Services Compensation Scheme (FSCS) up to £85,000 per person, per institution, so it's worth checking this limit if you're depositing a large lump sum. Interest earned outside of an ISA counts toward your Personal Savings Allowance, above which it may be subject to Income Tax — for larger deposits or higher AER, consider whether a Cash ISA (which is tax-free) might be a more suitable home for your savings.
AER stands for Annual Equivalent Rate. It shows what the interest rate would be if interest were paid and compounded once a year, making it easier to compare savings products that pay interest at different frequencies (e.g., monthly versus annually).
Usually not, or only with a penalty. Most fixed rate bonds don't allow access to your money during the term, or they charge a penalty such as loss of a number of days' or months' interest for early withdrawal. Check the terms of a specific bond before depositing funds you might need.
Deposits with UK-authorised banks and building societies are typically protected by the Financial Services Compensation Scheme (FSCS) up to £85,000 per person, per institution. If your deposit exceeds this, consider spreading it across different FSCS-protected providers.
Possibly. Interest from a standard (non-ISA) fixed rate bond counts toward your Personal Savings Allowance. If your total savings interest in a tax year exceeds your allowance, the excess may be subject to Income Tax at your marginal rate. A fixed rate Cash ISA pays interest tax-free instead.
No — the default is an example only. AERs on fixed rate bonds vary by provider, term length, and market conditions, and change frequently. Enter the actual AER offered by your provider for an accurate maturity value.
Longer terms typically (though not always) offer higher AERs, but they also lock your money away for longer. Try comparing different term lengths in this calculator alongside the rates currently on offer to weigh the trade-off between a higher rate and reduced access to your funds.
Disclaimer: The information, rates, and figures provided on this page are for educational and illustrative purposes only and do not constitute financial advice or a savings offer. The default AER is a sample value and does not reflect rates currently available from any specific bank or building society. Fixed rate bond terms, early withdrawal penalties, and tax treatment vary by provider and depend on your individual circumstances. Always check the full terms and conditions of a savings product and consult a qualified financial adviser if needed.