📈 Compound Interest Calculator

Watch your savings grow — initial sum, monthly contributions, and different compounding frequencies

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Investment Growth

Future Value—
Total Deposited—
Interest Earned—
Growth Multiple—

What is Compound Interest?

Compound interest means you earn interest on your interest — not just your original investment. Each period, your interest is added to your balance, and the next period's interest is calculated on that larger amount. Over time, this creates exponential growth.

The Rule of 72

Divide 72 by your interest rate to find how many years it takes to double your money. At 5%, your money doubles in approximately 72 ÷ 5 = 14.4 years. At 7%, it doubles in about 10 years.

💡 Einstein reportedly called compound interest "the eighth wonder of the world." The numbers back him up — £10,000 invested at 5% for 30 years grows to £43,219 with compound interest versus £25,000 with simple interest.

Monthly Contributions

Adding regular monthly contributions dramatically accelerates growth. In our calculator, £200/month alongside a £10,000 initial investment at 5% for 20 years produces a final value of approximately £138,000 — of which nearly £58,000 is interest earned. Without the monthly contributions, the final value would be only £26,500.