Free Compound Interest Calculator — Historical Reality Mode

Last updated: April 17, 2026

MoneyMath's compound interest calculator compares smooth return assumptions with historical-style market volatility, showing how contributions, timing, downturns, and dollar-cost averaging affect long-term growth.

Free to useRuns in your browserTransparent assumptions

Project investment growth from a starting balance, regular contributions, return rate, and time horizon.

Compare smooth returns with historical-style volatility to see why sequence and timing matter.

Use the contribution split to understand how much of the future balance comes from saving versus growth.

How to use this calculator

Step 1Enter your starting information. Add the core inputs requested by the Compound Interest Calculator, such as amounts, dates, rates, income, weight, or other scenario details.
Step 2Review the calculated result. Read the headline answer first, then scan the supporting breakdown, chart, or comparison table.
Step 3Compare another scenario. Change one input at a time to understand what drives the result and which option is most realistic.

Formula, Sources & Assumptions

Formula

Future value compounds the starting balance and adds recurring contributions at the selected interval.

Assumptions

Results are estimates for planning and education.
Actual costs, taxes, rates, or outcomes may differ based on personal circumstances and updated rules.