How to use the compound interest calculator
Enter the starting principal, annual interest rate, tenure in years plus optional months, compounding frequency, and an optional monthly contribution. Choose Calculate to see final amount, interest earned, and total invested. Use Copy results when you want the breakdown elsewhere. Nothing is uploaded. Figures assume a constant rate and ignore fees and taxes.
Frequently asked questions
How is compound interest calculated?
Without contributions, the final amount is A = P × (1 + r/n)^(n×t). P is principal, r is the annual rate as a decimal (percent ÷ 100), n is compounds per year, and t is time in years (years + months ÷ 12). Interest earned is A − P. When the rate is zero, the final amount equals the principal plus any contributions.
What compounding frequencies can I use?
Daily (365), monthly (12), quarterly (4), half-yearly (2), or yearly (1). Match the frequency your savings account, deposit, or investment quotes.
How do monthly contributions work?
Optional monthly deposits use the future value of an ordinary annuity at an effective monthly rate derived from your compounding setting. Total invested is principal plus all contributions; interest is final amount minus total invested.
Is this financial advice?
No. Results are planning estimates only. Real products may round differently, change rates, or charge fees. This page is not investment advice and not an offer.
Does the calculator upload my numbers?
No. Compound interest math runs in your browser. Deskutil never receives the principal, rate, tenure, contributions, or compounding you enter.