BEHIND THE NUMBERS
How this calculation works
Worked example
The starting £1,000 plus twelve £100 deposits gives £2,200. With zero interest and inflation, all of the balance is money you paid in.
Example result: £2,200.00
AER already includes compounding
An AER of 4% grows an untouched £1,000 to £1,040 over one year in this model. Dividing AER by 12 as though it were a nominal rate would slightly overstate the return.
Contribution dates matter
A payment made at the beginning of a month earns one extra month’s growth compared with the same payment at the end. The yearly table includes a final partial year when your saving period is not a multiple of 12 months.
Assumptions and rounding
- Constant monthly additions and constant rates. No withdrawals.
- Amounts use full precision until displayed.
Questions about this calculator
Can I model an investment rather than a savings account?
You can enter an assumed constant return after fees, but the projection does not represent market volatility or a guaranteed outcome.
Does this calculate savings tax?
No. Tax depends on your income, allowances, account wrapper and when interest arises. The balance shown is before any tax not already reflected in your entered rate.