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Regular saver calculator for irregular sums
strawb_shortcake
Posts: 3,206 Forumite
Pretty much as the title, how do I work out the interest for a regular saver when I haven't saved the same sum each month?
I know if you save the same amount then you add half the interest. I'm hoping there is a nice easy calculator as I'm rubbish at maths
I know if you save the same amount then you add half the interest. I'm hoping there is a nice easy calculator as I'm rubbish at maths
Make £2023 in 2023 (#36) £3479.30/£2023
Make £2024 in 2024...
Make £2024 in 2024...
0
Comments

In general you can calculate approximate interest by working out the average balance throughout the year and multiplying that by the interest rate  the average balance will typically be about half of the final balance (or six of the monthly payments) if being fed linearly, but if you're paying in different amounts then you immediately have a more complex calculation that doesn't lend itself to simplification. Is it relatively straightforward to figure out what your average monthly contribution is (and will be)?1

Roughly you could just apportion the interest rateI.e. say you have a 3% one£200 in Jan * 3%
£150 in Fan (11/12 of 3% is 2.75)
...
£250 in Dec x (1/12 of 3% is 0.25%)
This isn't completely accurate but it should give you the answer to the nearest £.0 
Another_Saver said:Roughly you could just apportion the interest rateI.e. say you have a 3% one£200 in Jan * 3%
£150 in Fan (11/12 of 3% is 2.75)
...
£250 in Dec x (1/12 of 3% is 0.25%)
This isn't completely accurate but it should give you the answer to the nearest £.3 
eskbanker said:Another_Saver said:Roughly you could just apportion the interest rateI.e. say you have a 3% one£200 in Jan * 3%
£150 in Fan (11/12 of 3% is 2.75)
...
£250 in Dec x (1/12 of 3% is 0.25%)
This isn't completely accurate but it should give you the answer to the nearest £.
In any event the amount you can make from regular savers is so small I cba working this out manually.1 
Thank you!
So I averaged putting £150pm away but fluctuating from £50250 a month.
I think, having read previous threads that I may be able to get a 13th payment in if I transfer on the 1st or 2nd of January. So I should end up with £2050 before interest
It's only 2% interest so isn't going to be much anyway, just thought I'd try and work it out in an effort to improve my understanding and maths skills.Make £2023 in 2023 (#36) £3479.30/£2023
Make £2024 in 2024...0 
So if you're averaging £150pm then the average balance over the year would be about £900, and therefore expected interest of roughly £18, perhaps £19. 13th payments can sometimes add pennies if you've optimised your payment dates and the provider allows and rewards them....2

eskbanker said:So if you're averaging £150pm then the average balance over the year would be about £900, and therefore expected interest of roughly £18, perhaps £19. 13th payments can sometimes add pennies if you've optimised your payment dates and the provider allows and rewards them....0

MaxiRobriguez said:eskbanker said:So if you're averaging £150pm then the average balance over the year would be about £900, and therefore expected interest of roughly £18, perhaps £19. 13th payments can sometimes add pennies if you've optimised your payment dates and the provider allows and rewards them....
I'm not interested in cutting more from my expenditure but I am already looking at ways to make money work harder, its only been the past year or so I've been in a position to save anything like I have done.Make £2023 in 2023 (#36) £3479.30/£2023
Make £2024 in 2024...0 
The interest is calculated daily on the balance on that day
So if you have a 3% Regular Saver then the interest rate per day is 3 / 365
You then use the formula each day:
balance = balance + balance x (3/36500)
1 
annabanana82 said:I save a fair bit more besides, this is the first year I've done a regular saver so it was purely down to curiosity not fretting about the possibility of an extra £20 come January.1
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