Compound Interest Calculator

See exactly how your money grows over time. Enter your starting balance, interest rate, and time horizon to calculate your future wealth — including the power of compounding frequency.

Final Balance
$0
Total Contributed
$0
Interest Earned
$0
Year Balance Contributed Interest Earned

How to Use This Calculator

Enter your starting balance, an optional monthly contribution, your expected annual return, and how many years you'll stay invested. Adjust the compound frequency if you like — for long-term investing the gap between monthly and daily compounding is small, so when in doubt leave it on monthly and focus on the rate and the timeline. Add an inflation rate to see what your balance is really worth in today's dollars.

Reading Your Results

Your total splits into what you put in versus what compounding added on top. Early on your contributions lead; the longer the timeline runs, the more the interest earned outpaces them — that crossover is compounding doing the work. Try pushing the time period up by five years and watch the final balance jump. It's the fastest way to feel why time matters more than the amount.

Why Compounding Frequency Matters

The more frequently interest compounds, the more you earn. Daily compounding produces slightly more than monthly, which produces more than annual. For most savings accounts and investments, monthly compounding is standard — but high-yield savings accounts often compound daily. In practice the difference is small next to your rate and your timeline, so don't over-optimize it.

Want to understand why these numbers behave the way they do — the Rule of 72, where compounding works for and against you, and how to actually start? Read the full guide: What Is Compound Interest? →

Frequently Asked Questions

What's the difference between compound and simple interest?

Simple interest is calculated only on your principal. Compound interest is calculated on your principal plus all previously earned interest. Over long periods, the difference is enormous.

What interest rate should I use?

For long-term stock market investments, the historical average annual return of the S&P 500 is approximately 7–10% (inflation-adjusted ~7%). For high-yield savings accounts, current rates range from 4–5%. For standard savings accounts, use 0.5–1%.

Does this calculator account for taxes?

No — this calculator shows pre-tax growth. In taxable accounts, you'll owe taxes on interest and dividends each year. In tax-advantaged accounts like a Roth IRA or 401(k), growth is tax-free or tax-deferred.

How does inflation affect my returns?

Inflation erodes purchasing power over time. A 7% nominal return with 2.5% inflation gives you a real return of approximately 4.5%. Use the inflation field above to see your inflation-adjusted balance.

How often does interest compound in real accounts?

Savings accounts typically compound daily or monthly. CDs often compound daily. Bonds usually pay semi-annually. Stock market returns compound based on reinvestment — most index funds reinvest dividends automatically.

Disclaimer: The content on Monetally is for informational purposes only and does not constitute financial, investment, tax, or legal advice. Always consult a licensed professional before making financial decisions. Full Disclaimer