Fixed Rate Bond Calculator United Kingdom

With a fixed rate bond you deposit a lump sum, agree to leave it untouched for a set term and the bank pays a rate fixed for the whole period. This calculator shows what your money will grow to by the end of the term and how much of that is interest, so you can compare offers before you lock anything away.

How a fixed rate bond works

You choose a term, commonly one, two, three or five years, and the provider guarantees the rate for the whole period. Unlike an easy-access account, the rate cannot be cut while your money is in the bond, which is the main attraction when rates look likely to fall. In exchange, most bonds do not let you withdraw before maturity, so the cash is genuinely tied up. Because the rate is known in advance, the final value is straightforward arithmetic.

Compounding annually versus interest at maturity

Bonds pay interest in different ways. A bond that compounds annually adds each year’s interest to the balance, so the next year you earn interest on a slightly larger sum. A bond that pays simple interest works out the whole amount on your original deposit and pays it once, at maturity. Over two years at the same rate the compounding version wins by a little; over five years the gap widens. Switch between the two in the calculator to see the difference for your figures.

Some providers offer a monthly-interest version of the same bond at a slightly lower rate, paying the interest into a linked account each month. That suits savers who want an income, but because the interest leaves the bond it does not compound, so the total return is usually a little lower. If you do not need the income, leaving the interest to compound is almost always better.

A worked example

You deposit £10,000 in a two-year bond at 4.5%. If interest compounds annually, the balance is £10,450 after a year and £10,920.25 after two, so you earn £920.25. With simple interest at maturity, you earn 4.5% of £10,000 twice, £900, for a maturity value of £10,900. Compounding is worth an extra £20.25.

Over five years at 4.5%, annual compounding takes the balance to about £12,462, roughly £2,462 of interest, while simple interest gives £2,250. Compounding is now worth about £212 more, nearly ten times the two-year advantage, which is why you should check how interest is paid before comparing headline rates.

How tax affects your take-home interest

The calculator shows interest before tax. Interest from an ordinary fixed rate bond counts towards your Personal Savings Allowance: £1,000 a year for basic rate taxpayers, £500 for higher rate taxpayers and nothing for additional rate taxpayers. Anything above it is taxed at your Income Tax rate. Many bonds pay all the interest at maturity, so a multi-year bond can put several years of interest into one tax year and take you over the allowance, even if each year’s share would have fitted. A cash ISA version keeps the interest tax-free, which can be worth a slightly lower rate.

What to check before you commit

Confirm whether interest is paid annually or at maturity, because two bonds with the same rate can pay different amounts. Check the minimum and maximum deposit, whether the account is protected by the Financial Services Compensation Scheme and what happens at the end of the term, since some bonds roll into a new product automatically unless you give notice. Note when the interest is paid, as that decides which tax year it counts in for your Personal Savings Allowance.

Common mistakes to avoid

The most common is locking away money you later need and finding the bond has no early access; keep a separate easy-access emergency pot first. Another is chasing the top rate from an unfamiliar provider without checking FSCS protection, which covers eligible deposits up to the current limit per person per banking licence; spreading larger sums across separate licences keeps everything protected. Many savers also let a maturing bond roll into the provider’s next product, which is rarely the best rate available. Note the maturity date and shop around a few weeks before it.

Assumptions and limitations

This is a planning estimate. It assumes the rate stays fixed for the term, that the deposit is a single lump sum at the start and that nothing is added or withdrawn. The annual option compounds exactly once a year; bonds that compound monthly or pay interest into a separate account will differ slightly. It does not deduct tax, so if your interest exceeds your Personal Savings Allowance the net figure will be lower. Read the bond’s own terms and treat the result as a guide.

About This Fixed Rate Bond Calculator

Use this fixed rate bond calculator to get an instant estimate based on the figures you enter. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.