Project your savings growth
Enter amounts in your selected currency. No currency conversion is applied.
Selected currency: GBP (£)
Growth over time
View breakdown
| Year | Total contributed | Interest earned | Ending balance |
|---|
Calculation methodology
The annual rate is a fixed nominal rate divided by 12 (a nominal annual rate divided by 12); interest is compounded monthly. The term is converted to the nearest whole month. Fees, taxes, inflation effects beyond the optional estimate, investment volatility and changing rates are excluded, so results are estimates rather than guarantees.
At the selected frequency, a contribution is made in the first applicable month and then every month, quarter or year. With start-of-month timing it is added before that month’s interest; with end-of-month timing interest is applied before it is added. The inflation-adjusted value uses nominal balance ÷ (1 + annual inflation rate / 12)months.
How to use the compound interest calculator
Build a shareable savings scenario, choose how often you contribute, and compare projected contributions with interest growth.
Choose a currency and enter amounts
Select the currency for this scenario; GBP (£) is the default and no currency conversion is applied. Enter your starting balance and the contribution amount in that currency.
Set frequency, rate and timing
Choose monthly, quarterly or annual contributions, then enter the fixed nominal annual rate and investment term. Select start-of-month contributions to add money before that month’s interest, or end-of-month to add it after interest.
Review and share the projection
Review the projected balance, total contributed, interest growth, and optional inflation-adjusted value. Use the growth chart and View breakdown table to explore the result by year; scenario inputs are retained in the shareable URL.
Frequently Asked Questions
What is compound interest?
Compound interest is growth calculated on the balance plus previously added interest.
How are contributions treated?
The calculator adds a contribution at the selected frequency. Start-of-month contributions are added before that month’s interest; end-of-month contributions are added after interest.
Does it include tax?
Fees, taxes, volatility, changing rates, and other real-world factors are excluded. You can optionally enter an inflation rate to estimate the final value in today’s money.
Are returns guaranteed?
No. The result is an illustration based on the rate you enter.
Can I change the investment term and frequency?
Yes. Enter a different term and choose monthly, quarterly, or annual contributions to compare projected balances and growth.
What does total contributed include?
It includes the opening balance and every regular contribution over the selected term.
Why does timing matter?
A start-of-month contribution is added before that month’s interest and therefore has longer to earn interest than an end-of-month contribution, which is added after interest.