Work out how much your savings could be worth. Enter a starting balance, a monthly payment and an interest rate to see the final balance and how much of it is interest.
Results
Final balance
£61,029.35
After 10 years at 4.5%, your savings grow to £61,029.35, of which £15,029.35 is interest.
Total deposits
£46,000.00
Total interest earned
£15,029.35
Annual equivalent rate (AER)
4.59%
DepositsInterest
Year-by-year breakdown
Year
Deposits
Interest
Balance
1
£13,600
£535
£14,135
2
£17,200
£1,259
£18,459
3
£20,800
£2,182
£22,982
4
£24,400
£3,313
£27,713
5
£28,000
£4,662
£32,662
6
£31,600
£6,237
£37,837
7
£35,200
£8,051
£43,251
8
£38,800
£10,113
£48,913
9
£42,400
£12,435
£54,835
10
£46,000
£15,029
£61,029
How this is calculated
The calculator works through your savings month by month.
Monthly rate. The yearly rate r is compounded n times a year (1 = annually, 12 = monthly, 365 = daily). It is turned into the equivalent monthly rate i = (1 + r/n)^(n/12) − 1, so twelve monthly steps give exactly the same yearly growth as the compounding frequency you chose.
Each month the balance grows by i, and your monthly payment is added at the start or end of the month.
Totals. Total deposits are your starting balance plus all monthly payments; total interest is the final balance minus total deposits.
For a single deposit with no further payments this is the standard formula A = P × (1 + r/n)^(n·t).
Worked example
You put £10,000 into savings and add £300 at the end of every month for 10 years at 4.5 % compounded monthly.
Your deposits add up to £10,000 + 120 × £300 = £46,000.
The final balance is £61,029.35, so you earn £15,029.35 in interest.
The starting £10,000 on its own would have grown to £15,669.93.
4.5 % compounded monthly is an AER of about 4.59 %.
Compound interest means you earn interest on your original savings and on the interest already paid into the account. Each time interest is added, the next payment of interest is calculated on a bigger balance, so savings grow faster over time.
What does AER mean?+
AER (annual equivalent rate) shows what the interest rate would be if interest were paid and compounded once a year. It lets you compare accounts that pay interest monthly, quarterly or annually. If you know an account's AER, enter it and choose annual compounding.
Does it matter how often interest is paid?+
A little. In the worked example below, monthly compounding earns about £15,029 in interest against £14,672 with annual compounding, roughly 2.4 % more. The rate and how long you save matter far more.
Is tax or inflation included?+
No. Results are before tax, charges and inflation. Interest outside an ISA can be taxable once it exceeds your Personal Savings Allowance, and inflation reduces what the final balance will buy.
Should I pay in at the start or end of the month?+
Paying in at the start of each month gives every payment one extra month of interest, so the result is slightly higher. Choose the option that matches when your money actually reaches the account.
How long will it take to double my savings?+
A rough rule is to divide 72 by the interest rate. At 4.5 %, savings double in about 16 years without further payments in. Set the monthly payment to zero to see the exact figure.
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