Compound Interest Calculator

See how your money grows with compounding and steady contributions. Set the rate, years, and timing to get a clear forecast—plus a year-by-year table and CSV export.

How to use Results explained Rules & assumptions FAQ

Inputs

All calculations run in your browser.

Results

Final balance

$0

Total contributions

$0

Total interest

$0
Optional ad slot

Yearly breakdown

YearStart balanceContributionsInterestEnd balance

CSV export includes all years.

How to use

  1. Enter your starting amount, annual rate, monthly contribution, and years.
  2. Pick a compounding frequency (e.g., monthly) and contribution timing (beginning or end of period).
  3. Hit Calculate. Review the summary, chart, and yearly table.
  4. Click Download yearly CSV to export the table for spreadsheets.

Tip: switching timing from “end” to “beginning” applies each contribution before interest, which usually boosts the final balance.

Rules & assumptions

FAQ

What’s the formula behind the calculator?

We iterate period-by-period. Each step applies interest at rate ÷ periods and adds a contribution either before or after interest depending on timing. The approach exactly matches an annuity-with-principal model and handles any frequency.

Which frequency should I choose?

Savings accounts are often compounded daily or monthly; investments are commonly viewed monthly. More frequent compounding increases the effective annual rate slightly.

Why does “beginning of period” give a higher balance?

Contributions start earning interest immediately each period, giving them more time in the market than end-of-period contributions.

Can I model irregular deposits or withdrawals?

This tool assumes steady monthly contributions. For irregular cash flows, export the CSV and adjust in a spreadsheet or use a cash-flow (XIRR/NPV) model.

Does this account for inflation or taxes?

No—figures are nominal. If you want a rough “real” view, subtract an estimated inflation rate from your APR or deflate the results externally.