How compound interest comparison calculator works
This calculator compares up to three savings or investment scenarios side by side so you can see which combination of principal, rate, compounding, horizon, and recurring deposit wins. Enter one scenario per line as label | principal | rate% | years | compounding-per-year | contribution | freq | timing, then press Compare.
Each scenario uses the standard compound-interest formula A = P(1 + r/n)^(nt) for the principal, plus the future value of a series for the recurring deposit. Deposits at the start of each period use the annuity-due form (multiplied by (1+r)); deposits at the end use the ordinary-annuity form. The effective annual percentage yield (APY) is (1 + r/n)^n - 1, which lets you compare rates fairly across different compounding frequencies.
The result shows the final balance, total contributions, total interest, and effective APY for every scenario, and highlights the one with the highest final balance. It is a planning estimate, not financial advice — real returns vary. Everything runs in your browser.
Frequently asked questions
How do I compare two investment scenarios?
Enter each scenario on its own line as label | principal | rate % | years | compounding-per-year | contribution | contribution frequency | contribution timing (start or end). Press Compare to see each scenario's final balance, contributions, interest, and APY, with the best final balance highlighted.
What is the difference between deposits at the start and the end?
Deposits at the start of each period (annuity due) earn interest for one extra period, so they produce a slightly higher balance than the same deposits at the end (ordinary annuity). Choose start to model contributions made at the beginning of each month or year.
What is effective APY?
APY (annual percentage yield) is the equivalent annual rate that accounts for compounding. It equals (1 + rate/compounding)^compounding - 1. Two scenarios with the same nominal rate but different compounding frequencies have different APYs, so APY lets you compare them fairly.
How many scenarios can I compare?
Up to three. The calculator highlights the scenario with the highest final balance. For a single scenario, enter one line and the result still shows the full breakdown.
