Project the future value of your investments with compound interest and regular contributions.
This calculator provides estimates for guidance only. Actual investment returns may vary. Past performance is not a reliable indicator of future results.
Understanding the future value of your investments is one of the most powerful tools in personal finance. Whether you are saving into a Stocks and Shares ISA, building a pension pot, or simply putting money aside in a high-interest savings account, knowing how compound interest works over time helps you set realistic goals and stay motivated. The concept is straightforward: money invested today grows not just on the original amount, but on the accumulated interest as well. This is compound interest, and it is the reason why starting early matters so much. A 25-year-old who invests GBP 5,000 and leaves it for 40 years at 7% will end up with roughly GBP 74,872, while starting at 35 with the same amount gives only GBP 38,061. That extra decade of compounding nearly doubles the result. This calculator lets you project the future value of a lump sum investment, with optional regular monthly contributions. You can compare different compounding frequencies (annually, quarterly, monthly, or daily) to see how compounding speed affects your total returns. The stacked area chart breaks down your total into contributions and interest earned, making it easy to visualise how much of your future wealth comes from growth rather than deposits. For UK investors, common scenarios include projecting ISA growth (currently up to GBP 20,000 annual allowance), estimating workplace pension outcomes, or modelling the long-term impact of regular savings into index funds. The calculator uses precise Decimal.js arithmetic to avoid floating-point rounding errors that can accumulate over long time horizons.
To use the future value calculator: 1. Enter your Present Value. This is the lump sum you are investing today. If you are starting from scratch, enter 0. 2. Set the Annual Interest Rate. For a Cash ISA, use the advertised rate (typically 3-5%). For equity investments or index funds, 7-8% is a common long-term assumption. Be conservative with your estimates. 3. Choose the Investment Period in years. Longer periods amplify the effect of compounding dramatically. 4. Optionally enter a Monthly Contribution. This represents regular savings you will add each month. Even small amounts compound significantly over decades. 5. Select a Compounding Frequency. Most savings accounts compound daily or monthly. Bonds and fixed-rate products often compound annually or semi-annually. 6. Review the results. The Future Value shows your projected total. Total Contributions shows how much you actually deposited. Total Interest Earned shows the pure growth from compounding. The chart visualises the split between your money and the market's money over time.
The future value calculation uses two components: 1. Future Value of a Lump Sum: FV = PV x (1 + r/n)^(n x t) Where PV = present value, r = annual rate (decimal), n = compounding periods per year, t = years. Example: GBP 5,000 at 7% compounded monthly for 20 years: FV = 5000 x (1 + 0.07/12)^(12 x 20) = 5000 x (1.005833)^240 = GBP 20,193.69 2. Future Value of Regular Contributions (Annuity): FV = PMT x [((1 + r/n)^(n x t) - 1) / (r/n)] Where PMT is the contribution per compounding period. For monthly contributions with monthly compounding, PMT is simply the monthly amount. For other frequencies, contributions are adjusted proportionally. 3. Total Future Value = FV of Lump Sum + FV of Annuity The total contributions are calculated as: PV + (monthly contribution x 12 x years). Interest earned is the difference between the future value and total contributions. The compounding frequency matters because more frequent compounding means interest starts earning interest sooner. Annually compounds once per year, quarterly four times, monthly twelve times, and daily 365 times. The effective annual rate increases with compounding frequency, even if the nominal rate stays the same.
UK investors should consider tax-efficient wrappers when projecting future values. ISAs (Individual Savings Accounts) shelter up to GBP 20,000 per year from income and capital gains tax, making the projected returns more realistic since you keep the full amount. Workplace pensions benefit from employer contributions and tax relief, effectively boosting your contribution rate. For investments outside tax wrappers, remember that capital gains tax and dividend tax will reduce your actual returns. Our ISA Calculator and Pension Calculator can help model these specific scenarios. For comparing the annualised return of an investment you have already made, try our CAGR Calculator.