Regular Saver Calculator United Kingdom

This regular saver calculator shows the maturity value and interest on a UK regular saver, where monthly deposits earn roughly half the headline rate.

What it does

The Regular Saver Calculator shows the true maturity value of a UK regular saver account. Because you pay in monthly rather than as a lump sum, interest is earned on a balance that only reaches its full size in the final month — so the money you actually earn is roughly half of what the headline rate suggests.

Data sources & parameters

This calculator uses standard financial formulas and runs entirely in your browser. It needs no external rate data — your result is computed only from the values you enter above.

We always strive to use the latest data for every variable so our results and reports are as accurate as possible. Even so, errors are possible — you should not rely on this tool or its report alone, and we accept no liability for any decision made based on it.

The formula

With monthly rate i = rate ÷ 100 ÷ 12 over m months: maturity = deposit × ((1 + i)^m − 1) ÷ i × (1 + i); interest = maturity − (deposit × m)

How it works

It treats each monthly deposit as landing at the start of the month (an annuity due) and compounds the account balance monthly at the headline rate divided by twelve. It then subtracts everything you paid in to reveal the interest earned.

Where it is used

Comparing a headline regular saver rate against the interest you would really receive
Planning how much to drip in each month to hit a savings target
Sense-checking a bank's advertised return before opening an account

Worked example

Paying in £300.00 a month at 6% for 12 months gives a maturity value of … — you deposited … and earned … in interest.

Regular saver accounts often top the UK best-buy tables with rates well above easy-access accounts. You cannot deposit a lump sum: you pay a fixed amount in each month, and interest is earned only on the balance built up so far. This calculator applies the rate to your monthly deposits the way a real account does, so you can see the maturity value and the interest you will receive.

Why the headline rate is misleading

A 6% rate sounds as if it should turn £3,600 of savings into about £216 of interest. It does not, because of timing. You start the year with nothing and finish with the full balance. Your first deposit earns interest for the whole term, but your final deposit is in the account for only a few weeks before it matures. Averaged across every payment, your money spends only about half the term earning interest, so the return on your total deposits comes out close to half the advertised AER. The rate describes interest on a balance, not on the sum of your contributions.

How the calculation works

Each deposit is treated as arriving at the start of its month, and the whole balance compounds monthly at the annual rate divided by twelve. Each month the balance grows by that rate, a new deposit is added, and the process repeats for the length of the account. This is an annuity due, and it reduces to one formula: the deposit multiplied by ((1 + i) to the power of the number of months, minus one), divided by the monthly rate, then multiplied by (1 + i) for the early-month timing. At a zero rate the formula returns your total deposits.

A worked example

Take a common best-buy shape: £300 a month at 6% over twelve months. You pay in £3,600. The monthly rate is 0.5%, and the annuity-due calculation gives a maturity value of about £3,719, or roughly £119 of interest rather than the £216 the headline rate might suggest. The £119 is still worth having, and it is usually tax-free within your Personal Savings Allowance.

Getting the most from a regular saver

The early deposits earn the most, so pay in every month: a skipped payment loses that month of interest for good. Many accounts set a monthly maximum, and paying the full amount earns the rate on the largest possible balance. When the account matures, usually after twelve months, the balance typically moves to a much lower rate, so move the matured pot into a better account and open a new regular saver for the next year.

Assumptions and limitations

This is a planning estimate. It assumes an equal deposit every month, a constant rate for the whole term, and monthly compounding with deposits at the start of each month. Real accounts may pay interest annually, may cap the monthly deposit and may change the rate if it is variable. The calculator does not deduct tax, though interest within your Personal Savings Allowance or inside a cash ISA is usually tax-free. It does not model missed payments or withdrawals, both of which reduce the final figure. Check the terms of the account before you open it.

About This Regular Saver Calculator

Use this regular saver 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.

Frequently asked questions

Why do I earn less than the headline rate on a regular saver?

Because you pay money in gradually. The rate applies to your balance, and for most of the term the balance is only part of the final total. Your first deposit earns interest for the whole term and your last for barely a month, so the return on the money you have paid in works out at roughly half the advertised rate.

What is the difference between the maturity value and the interest earned?

The maturity value is everything in the account on the day it matures: your deposits plus the interest. The interest earned is the maturity value minus your total deposits. The calculator shows both, so you can see how much of the final pot is your own money.

Does this calculator assume deposits at the start or end of the month?

The start of each month, known as an annuity due. Most UK regular savers take a standing order early in the month, so each deposit earns a full month of interest. This gives a slightly higher result than end-of-month payments.

What rate should I enter?

The AER your bank advertises for the account. There are no built-in rates, because regular saver rates change often and vary by provider. The calculator divides the rate by twelve for each month, which for a fixed annual rate gives a result a few pence above the exact AER figure.

What happens when the regular saver matures?

Most regular savers run for twelve months and then close or move the balance into an easy-access account at a much lower rate. To keep a high rate you usually have to open a new regular saver each year. Set the number of months to match your account term.

About the author

Written and reviewed by

Taha Kheirandish

Economics student and independent researcher

Taha Kheirandish reads tax codes the way other people read maps — to find out where a system actually leads, not where it claims to go.

He is an economics student, and his work here is comparative by design. A pension deferral bonus in Quebec, a commuting allowance in Germany, a rent-increase ceiling in the Netherlands: each is a decision a government made about how money should move, and each reads differently once you set it beside eight others. He builds and checks these calculators across nine markets from primary sources — the regulation rather than a summary of it, the ministry’s own circular rather than a news item quoting it.

That is the editorial standard of the site as well as his habit. Every rate, threshold and bracket here carries the document it was read from and the date it takes effect, and gets re-checked when the law moves rather than when someone happens to notice.

He is a researcher, not a licensed adviser, and nothing on this site is personal financial advice. It is arithmetic done carefully with its sources shown — so that you can check it, and take it to someone who is.

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