A compound interest and savings-goal calculator that projects the future value of your savings or investments — including regular monthly deposits, your choice of compounding frequency, and an optional inflation adjustment. Useful for planning an ISA, a pension top-up, an emergency fund or any long-term savings goal.
How it works
The tool compounds period by period. Your annual rate r is divided by the compounding frequency n (yearly = 1, quarterly = 4, monthly = 12, daily = 365) to get a per-period rate. Each period it applies:
balance = balance × (1 + r⁄n) + contribution per period
where the per-period contribution is your monthly amount × 12 ÷ n. After (years × n) periods it reports the future value, the total you contributed (starting amount plus all deposits) and the interest earned (the difference). If inflation is on, it divides the future value by (1 + inflation)^years to show the result in today’s money.
Example
Start with £1,000, add £100/month, at 5% compounded monthly for 10 years:
- Future value: about £17,200
- Total contributed: £13,000 (£1,000 + £12,000 of deposits)
- Interest earned: about £4,200
Turn on 2.5% inflation and that £17,200 is worth roughly £13,400 in today’s purchasing power.
| Monthly deposit | Rate | Years | Future value |
|---|---|---|---|
| £100 | 5% | 10 | £17,200 |
| £200 | 5% | 10 | £32,000 |
| £100 | 7% | 20 | £53,300 |
| £250 | 6% | 30 | £253,000 |
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