Regular saver calculator
Enter your monthly deposit and interest rate to see exactly what you’ll earn, including why regular savers pay less than the headline AER suggests.
Written by William Haymonds, MoneyHQ founder and deal editor. Last reviewed . How we check deals
You need: A monthly amount and a rate. Nothing you type leaves this page.
What do you want to know?
Interest earned
- You pay in (£200 a month)£2,400
- Interest£51.69
- You end with£2,452
Each monthly payment earns interest for the months it is in the account, worked out month by month rather than with a shortcut factor. Before any tax. Check whether tax applies to you.
The same money on the best rate we have verified
Santander, Regular Saver (Regular saver). £51.09 more than at 4% over a year. Checked against the provider's own page.
Tell me when a verified rate beats 4%
We check every rate on our shelf against the provider's own page. When one we have verified passes the rate you typed, you get one email with the account.
What counts as a good rate right now? Santander’s Regular Saver is paying 8.00% AER (verified by MoneyHQ on 17 October 2026). At £200 a month over 12 months, that’s around £103 in interest before tax. The calculator above uses whatever rate you enter, so you can compare it directly.
→ See the top-paying regular savers MoneyHQ has verified
Accurate as of 17 October 2026
The working behind the figure, with the maths shown rather than a shortcut.
How the calculator works
Regular savers don’t work like ordinary savings accounts. You’re not depositing a lump sum on day one but instead you’re paying in month by month, so each deposit earns interest only for the time it has left in the account. A payment made in month twelve earns interest for one month. A payment made in month one earns interest for twelve. The average balance across the year is roughly half what you eventually pay in.
The calculator accounts for this properly. It applies compound interest to each monthly deposit individually, then totals them. The AER figure from the provider assumes a full year at the headline balance which is why the interest you earn is lower than multiplying your total savings by the AER.
Regular saver vs easy access which pays more?
It depends whether you already have the money or you’re saving from income.
If you’re saving fresh money each month, a regular saver at 8% will almost always beat an easy-access account at 5%, even though the effective return on a regular saver is roughly half the headline rate (because of the example below).
If you have a lump sum sitting somewhere already, drip-feeding it into a regular saver is usually slower than putting it straight into a competitive easy-access account. Run both scenarios in the calculator above to check.
An example: why William earns less than he expects
William saves £200 a month for a year (£2,400 in total) into a regular saver paying 6% AER.
Quick guess: 6% of £2,400 = £144 interest.
Why that’s wrong: William didn’t have £2,400 sitting there from day one. In January he had £200. In June he had £1,200. He only hit the full £2,400 in December. Interest is calculated on whatever’s in the account each month.
His average balance across the year was around £1,200 (half of £2,400), because the pot built up gradually. So, a realistic estimate is 6% of £1,200 = £72 interest, not £144.
The rough rule: expect to earn about half what the headline rate implies on your total deposits.
The calculator above works it out precisely, but that halving rule is a useful sense-check before you open anything.
Why does my regular saver earn less than the headline rate?
Because you’re not holding the full balance for the whole year. Each monthly payment earns interest only from the day it goes in. If you pay in £200 a month for 12 months, your first £200 earns interest for 12 months but your last £200 earns interest for just one month. The average balance is in the account for roughly half the year, so your effective return is around half the advertised AER.
What is the best regular saver rate right now?
Santander’s Regular Saver is paying 8.00% AER as of 17 October 2026, verified by MoneyHQ. Several providers offer 5% to 8% AER. You can see the full verified list on MoneyHQ regular savers.
Can I pay a lump sum into a regular saver?
Most regular savers don’t allow it as they’re designed for monthly payments up to a set cap (typically £200 to £300 a month). Some accounts close or stop paying the bonus rate if you miss a month or overpay. Check the terms before opening.
What happens to my money at the end of the year?
Most regular savers convert to an ordinary savings account at a much lower rate when the 12-month term ends. It is worth setting a reminder to move the money.
Is the interest taxed?
Yes, savings interest is taxable income. Most people have a Personal Savings Allowance (£1,000 a year for basic-rate taxpayers, £500 for higher-rate, £0 for additional-rate.) The calculator has an optional tax band input if you want an after-tax figure.