Compound Interest Calculator

Project the exponential growth of your savings and monthly contributions over any time horizon.

Year Total Deposits Interest Earned Total Balance

How Does Compound Interest Work?

Compound interest is the addition of interest to the principal sum of a loan or deposit, or in other words, interest on interest. Over time, compounding yields exponential curve growth rather than linear growth. Standard accounts only earn interest on simple principal deposits. High-yield savings, stock index portfolios, and pension schemes compound continuously, multiplying balances exponentially.

The Formula for Growth Projections

This calculator tracks growth using an iterative monthly compound interest schedule:

A = P(1 + r/n)^(nt) + PMT * [((1 + r/n)^(nt) - 1) / (r/n)] * (1 + r/n)

Where A is the final balance, P is the initial principal, r is the annual rate, n is the compound frequency (12 times per year for monthly calculations), and PMT is the monthly contribution.

How to Use

  1. Enter your initial investment inside the **Initial Principal** input box.
  2. Specify the regular contribution amount added each month.
  3. Set the target **Annual Interest Rate** and desired **Time Horizon** in years.
  4. Click **Calculate Growth** to view your projected assets. The interactive Chart.js canvas details the visual gap between total deposits and interest over time.