Compound Interest Calculator
Project compound growth with monthly contributions
Quick guide
What can Compound Interest Calculator help you do?
Estimate future value and total contributions using an initial balance, end-of-month deposits, annual rate, years, and compounding frequency.
Best for
Compare an initial balance and regular monthly contributions under a constant assumed annual rate. Changing the contribution, duration, or compounding frequency reveals how those assumptions affect the ending balance. This is a mathematical scenario, not a quotation for a savings or investment product.
How to use it
Defaults are 1,000 principal, 100 monthly, 7% annually, 10 years, and 12 compounds per year. Amounts must be nonnegative with at least one positive. Use a rate above -100%, a duration representing whole months up to 200 years, and an integer frequency from 1 to 365.
How to read the result
Future value includes growth on the principal and deposits made at each month end. Total contributions excludes growth; subtract it from future value to find modeled gain or loss. Monthly deposits use fractional compounding exponents for their remaining time, even when the selected frequency is annual.
Privacy and limits
This calculator branch processes balances, contributions, and rates in the browser. It does not connect to financial accounts, fetch market quotes, or save a portfolio. Hypothetical amounts are sufficient; no statements or account identifiers are needed. This describes the calculator, not every connection made by the website.
The model excludes fees, taxes, inflation, exchange movements, and withdrawals. It is not investment advice or a return guarantee. Extreme values can produce a dash instead of an amount, and some fractional year entries can fail the whole-month check; neither outcome means a zero return.
Frequently Asked Questions
Is this tool free?
Yes. It runs in your browser and does not require sign-in.
Is the result exact?
The result is a practical estimate or conversion. For tax, medical, legal, or financial decisions, verify with a qualified source.