Calculate how your investments grow over time with the power of compounding. Enter your principal amount, monthly contribution, expected annual return rate, and investment horizon to see exactly how much your money can grow. Compound interest is the most powerful wealth-building tool available to everyday investors, turning consistent small contributions into substantial long-term wealth.
Total Investment Value
£343,778
Total Invested
£130,000
Total Returns
£213,778
164% gain
Key Insight: Your £10,000 grows to £343,778 in 20 years. That's £213,778 earned from compounding alone —164% return on investment.
Compound interest is the process where the interest you earn on an investment also earns interest over time. Unlike simple interest, which only applies to your original principal, compound interest applies to both your principal and accumulated interest. This creates an exponential growth curve that accelerates over longer time periods.
The formula for compound interest with regular contributions is: A = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)], where P is the principal, r is the annual interest rate, n is the number of compounding periods per year, t is time in years, and PMT is the periodic contribution.
Consider this example: if you invest £8,000 at 8% annual return and add £400 monthly for 30 years, you would contribute a total of £152,000 out of pocket. However, with compound interest, your investment would grow to approximately £668,000. That means compounding generated over £516,000 in pure returns — more than three times your total contributions.
Start early — even small amounts benefit enormously from time. Increase contributions regularly as your income grows. Choose investments with higher expected returns for long-term goals. Reinvest all dividends and interest rather than withdrawing them. Avoid frequent withdrawals that interrupt the compounding cycle.
Simple interest calculates returns only on the original principal. A £8,000 investment at 8% simple interest earns £640 per year regardless of how long you hold it. With compound interest, that same investment earns £640 in year one, but continues accelerating. Over 30 years, the difference between simple and compound interest on this example exceeds £72,000.