Compound Interest Calculator
Scenario examples are editable assumptions, not return forecasts.
Investment Inputs
RESULT
Growth Over Time
Annual Breakdown
| Year | Opening Balance | Contributions | Interest Earned | Closing Balance |
|---|
Formula & Assumptions
Monthly rate = annual rate ÷ 12
Balance = prior balance × (1 + monthly rate) + contribution
Real value = future value ÷ (1 + inflation)years
For nonmonthly compounding, monthly contributions use an equivalent monthly growth rate: (1 + annual rate / n)n/12 − 1. This is a mathematical convention; actual account crediting rules may differ. No taxes, fees, rate changes or withdrawals are modeled.
Frequently Asked Questions
How does compounding grow my savings?
Each period’s interest becomes part of the balance and can earn interest in later periods. This simulation uses the fixed rate you enter; actual investment returns can vary and may be negative.
How does contribution timing affect results?
Beginning-of-month contributions receive one extra month of growth compared with end-of-month contributions. Deposited totals remain the same.
What does inflation-adjusted value mean?
It estimates the final balance in today’s purchasing power using the entered annual inflation assumption. It is not the same as subtracting nominal contributions from the final balance.
Does switching currency convert my investment?
No. The currency selector changes display labels; it does not apply an exchange rate.
Do FIRE and retirement modes predict readiness?
No. Retirement mode enables the inflation view; FIRE adds a nominal goal and reports when the projection first reaches it within the entered horizon. Neither mode models withdrawal sustainability, pensions, taxes or spending needs.
Compound Interest Calculator — free online calculator.