How often should interest compound?

The more frequently interest compounds, the more you earn. Daily compounding earns slightly more than monthly, which earns more than annual. The difference becomes significant over long periods. Most savings accounts compound monthly or daily.

What's the Rule of 72?

The Rule of 72 is a quick estimate: divide 72 by your annual interest rate to find how many years it takes to double your money. At 8% interest, your money doubles every 9 years (72 ÷ 8 = 9). At 6%, every 12 years.

What return rate should I use for stocks?

The S&P 500 has historically averaged about 7–10% annual returns (inflation-adjusted 7%). Past performance doesn't guarantee future results, but 6–8% is a common conservative estimate for long-term stock market investments.

Does this include regular contributions?

This calculator shows growth on a lump-sum investment. If you're making regular monthly contributions (like a 401k), multiply your monthly contribution by [(1+r)^n - 1]/r to calculate the future value of those additions separately.

Compound Interest Calculator — Free Investment Growth Tool

The Compound Interest Calculator shows you the power of compounding — how your money grows exponentially when interest is earned not just on your initial principal but also on all previously accumulated interest. Einstein allegedly called compound interest the 'eighth wonder of the world.' Whether you're investing in a savings account, stocks, or retirement fund, understanding compound growth is essential for building long-term wealth. Enter your starting amount, interest rate, and time horizon to see your future value.

Initial Investment($)

Annual Interest Rate(%)

Time Period(years)

Compounding Frequency

Frequently Asked Questions

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (calculated only on principal), compound interest grows exponentially over time — the longer you invest, the faster it grows.

Related Calculators

💰Mortgage Calculator 💰Loan EMI Calculator 📐Percentage Calculator

Start investing and let compound interest work for you. Open a brokerage account today.

Start Investing