Yield Theory
Sign inSubscribe

Calculator

Compound Interest Calculator

See how an investment grows when returns compound over time.
Future value
$343,778
Total contributed
$130,000
Interest earned
$213,778

Compound interest is the engine behind long-term investing: your returns earn returns of their own. This calculator projects how a starting balance plus regular contributions can grow at a given annual rate, compounded over time. Adjust the inputs to see how starting earlier or contributing more changes the outcome.

Frequently asked questions

What is compound interest?

Compound interest is interest calculated on both your original principal and the interest already added to it. Over long periods this creates exponential, rather than linear, growth.

How often should returns compound?

More frequent compounding produces slightly higher results, but the annual rate and time horizon matter far more. For long-term stock investing, annual compounding is a reasonable approximation.

What return rate should I assume?

Historically, broad US equity indices have returned roughly 7–10% annualized over long horizons before inflation, but future returns are not guaranteed. Use a conservative estimate and test a range.

More calculators

Dollar-Cost Averaging CalculatorProject the outcome of investing a fixed amount at a regular interval.CAGR CalculatorCalculate the compound annual growth rate between two values.Rule of 72 CalculatorEstimate how long it takes an investment to double.Inflation & Purchasing Power CalculatorSee what today's money will be worth in the future.Position Size CalculatorSize a trade based on how much you're willing to risk.

Go deeper

Investing glossaryUnderstand the conceptsStock researchApply it to real names

The math is easy. The macro is hard.

Yield Theory does the macro research so you can act with conviction — where capital is heading, and what to do about it. Founding price $24.99/mo.

Get instant access →

$24.99/mo · cancel anytime · researched by humans