Compound Interest Calculator — APY, Schedule & Growth

Calculator

Currency (display only) Initial investment Interest rate (%) Rate is quoted as Compound frequency Years Months (0–11) Regular contributions Contributions at beginning or end of each period?

How to use this calculator

Enter your starting balance and the interest rate. Use the “rate is quoted as” field if your rate is daily, weekly, monthly, or quarterly instead of yearly.
Pick how often interest compounds (daily, monthly, yearly, or a custom number per year).
Set the term in years plus extra months (0–11).
Optionally add regular deposits or withdrawals, timing, and yearly increases.
Click Calculate to see future value, total interest, effective annual rate, return metrics, and schedules.

Why use a compound interest calculator?

Compounding means interest earns interest. This tool helps you compare scenarios (rate, frequency, and contributions) before you save or invest. Figures are illustrative; real products may use different day-count rules or fees.

Frequently asked questions

How is the effective annual rate (APY) calculated?

We use the nominal annual rate you enter (scaled by whether you quoted it as daily, weekly, monthly, quarterly, or annual), then apply the standard effective rate: (1 + r/n)^n − 1, where n is how many times interest compounds per year.

When are deposits and withdrawals applied?

You choose beginning or end of each contribution period. The engine steps month by month, applies your scheduled flows, then accrues interest for that month using a rate equivalent to your compounding frequency.

Why does my result differ slightly from another website?

Rounding, day-count conventions (360 vs 365), and exact timing of contributions can differ. We use a uniform monthly accrual that matches the nominal rate and compounding count you select—close to major public calculators for the same inputs.