Compound Interest Calculator
See how a starting balance and optional monthly contributions grow over time — enter your numbers to get your final balance, total contributions and total interest earned.
Estimate only. This is an estimate — representative figures, not financial advice. Actual interest rates vary and this calculator doesn't account for tax on your returns. Speak to a financial adviser before making investment decisions.
Enter your savings details
Your final balance, total contributions and total interest earned appear here as you type.
How compound interest is calculated
Compound interest is interest earned on both your original balance and the interest it has already earned, so growth accelerates over time. This calculator uses the standard future-value formula: FV = P·(1+i)ᴺ + C·[((1+i)ᴺ − 1)/i], where P is your starting balance, C is your regular contribution, i is the interest rate per period and N is the number of periods. If you add a monthly contribution, the projection compounds monthly, since deposits happen every month; with a lump sum only, you can choose monthly or annual compounding. This is a projection based on a fixed rate — real savings rates change over time and this figure ignores tax.