Compound Interest Calculator

Compound interest is when you earn interest not only on your principal but also on previously accumulated interest. It grows much faster than simple interest over the long term, which is why it's often called the 'magic of compounding.'

Divide 72 by your annual return rate to estimate how many years it takes to double your money. For example, at 7% annual return: 72 ÷ 7 ≈ ~10 years to double your principal.

Keep your investment period as long as possible and avoid withdrawals. A higher return rate and shorter compounding periods (monthly > annually) also significantly boost the effect.

With a ₩10M principal at 7% annually over 20 years: simple interest gives ₩24M, while compound interest yields approximately ₩38.7M. The gap grows exponentially over time.

Yes. Each periodic contribution earns compound interest individually. However, later contributions benefit less because they have a shorter compounding period than earlier ones.

Real return ≈ Nominal return − Inflation rate. If you earn 7% annually with 3% inflation, your real return is about 4%. For long-term planning, use the real return rate for a realistic projection.

Taxes such as dividend income tax (15.4%) and financial investment income tax reduce your effective return. Calculating with an after-tax return rate gives more accurate results. Tax-advantaged accounts like ISA or pension savings can reduce the tax burden.