Decision tools built for clarity
Compound Interest Calculator
Explore how contributions and compounding can affect long-term growth.
Enter the starting principal, recurring contribution, annual rate, duration, compounding frequency, contribution frequency, timing, and currency.
This educational growth projection is not financial or investment advice and does not guarantee any return.
Methodology
Formula or transformation
Accumulates principal and recurring contributions across the selected compounding and contribution periods.
Variables
- Starting principal
- Recurring contribution
- Annual interest rate as a percentage
- Duration in years
- Compounding periods per year
- Contribution periods per year
- Contribution timing within each period
Units
- Currency
- Percent
- Years
- Periods per year
Rounding policy
Displayed money values are rounded to the declared currency scale using half away from zero.
Interest is credited at the selected compounding interval, while contributions are applied at the selected frequency and beginning-or-end timing.
Explore how contributions and compounding can affect long-term growth.
Reviewed sources
- Investor.gov / U.S. SEC — Compound interest calculator methodology Reviewed on 2026-09-08
Formula review history
-
Initial formula and source review.
Reviewed 2026-09-04 for formula version periodic-compounding-contributions-v1
Assumptions
- The entered annual rate and contribution amount remain constant.
- Compounding and contribution timing follow the selected fixed schedules.
Limitations
- Taxes, fees, inflation, withdrawals, and market volatility are excluded.
- Actual investment returns vary and are not guaranteed by a constant-rate projection.
Worked example
A principal of 1,000 compounded annually at 5% for 2 years with no contributions grows to 1,102.50.
Frequently asked questions
Does contribution timing matter?
Yes. A beginning-of-period contribution generally compounds for longer than an end-of-period contribution.
Is the projected balance guaranteed?
No. It is a constant-rate mathematical projection, not a forecast or investment promise.