Compound Interest Calculator

See how your savings and investments grow over time with compound interest and regular monthly contributions.

Your Investment

The amount you're starting with today (use 0 if starting from scratch)

Added at the end of each month and compounded going forward

S&P 500 ~10% historically; 7% is a common inflation-adjusted estimate

Your investment time horizon

Good lending options, competitive rates

Your Projection

Future value in 20 years

$0

at 7% annual return, compounded monthly

Total Contributions
$0
Interest Earned
$0
Annual Return Rate
7%

Contributions vs. Interest Earned

Money you put in (0%)Compound growth (100%)

Assumes monthly compounding with contributions added at the end of each month. Actual returns vary year to year.

✅ Excellent Credit — Compounding Is on Your Side

With excellent credit you're paying minimal interest on debt, which leaves more to invest. The longer your money compounds, the more powerful it becomes — see how it adds up for retirement with our retirement calculator.

Understanding Compound Interest

What Is Compound Interest?

Compound interest is interest earned on both your original money and the interest it has already earned. Over time this snowball effect accelerates — the longer your money stays invested, the larger the share of growth that comes from interest rather than your own contributions.

Time Beats Timing

Starting early matters more than starting big. A dollar invested today has decades to compound, while a dollar invested later has only a few years. Even modest monthly contributions can grow into a substantial sum given enough time.

The Cost of High-Interest Debt

Compounding works in reverse on debt. Every dollar paid in credit card or loan interest is a dollar that can't compound for you. Improving your credit or consolidating debt frees up cash that can be invested instead.

Choosing a Return Rate

The U.S. stock market has historically returned roughly 10% per year before inflation, or about 7% after. Conservative savers may use 4–5%; this calculator lets you model any rate so you can compare optimistic and cautious scenarios.

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