Compound Interest Calculator

How It Works

Compound interest estimates growth by applying the interest rate repeatedly over time. This calculator uses monthly compounding: it adds your monthly contribution, applies the monthly rate, and repeats that process for the selected number of months. The result separates your own contributions from estimated interest so you can see how much growth comes from compounding versus saving more money.

Example

If you start with $10,000, earn 7% per year, and add $200 every month for 10 years, the calculator estimates the final value and separates your own contributions from the interest earned. Try lowering the rate or shortening the term to see how sensitive long-term growth can be.

When to use this calculator

• Use it when you want to compare long-term savings scenarios with different rates and monthly contributions.
• Use it before talking to an advisor or bank so you already understand the rough scale of possible outcomes.
• Use it when deciding whether time, rate, or monthly saving discipline matters more in your plan.

Inputs that matter most

• Starting amount sets the initial base for growth.
• Annual interest rate has a large long-term effect, so test conservative and optimistic scenarios.
• Years controls how many compounding cycles occur.
• Monthly contribution shows how consistent saving changes the final value.

How to use the estimate responsibly

• Run at least three scenarios: low rate, expected rate, and high rate.
• Do not ignore taxes, inflation, account fees, or withdrawal rules.
• Use the result as planning context before checking real quotes or professional advice.

Currency display note

• Currency display changes formatting only.
• The calculator does not convert exchange rates.
• Enter all money inputs in the same real currency before comparing results.