Compound Interest Calculator

Calculate compound results from initial amount, monthly contribution, rate, and period.

Note: A financial reference simulation. Returns are not guaranteed and it may not reflect taxes, fees, product terms, or market changes.

Category: Calculators

When to use?

Use it to simulate the compounding effect of long-term investing or saving, or to back-calculate the monthly contribution needed to reach a target amount.

How to use

  • Enter the initial investment amount.
  • Enter the monthly contribution.
  • Enter the annual return (%) and period (years).
  • The compound result and the principal/interest split are shown.

Input Explanation

Enter the initial principal, monthly additional contribution, annual return, and investment period (years).

Calculation Basis

Compound: principal × (1 + monthly rate)^months + monthly contribution × [(1 + monthly rate)^months − 1] ÷ monthly rate.

Usage Examples

  • Simulate long-term investing - Estimate a future amount from monthly contributions and an annual return.
  • Plan target funds - Gauge the monthly contribution or period needed to reach a target amount.
  • Compare compounding - Vary the return or period to see how compounding affects the result.

Examples

  • Initial 10,000,000, 500,000/month, 7%/yr, 10 yrs → ~116,000,000 (principal 70,000,000, interest 46,000,000)
  • Initial 0, 300,000/month, 5%/yr, 20 yrs → ~123,000,000 (principal 72,000,000)

Cautions

  • A simple calculation assuming the entered return holds. Actual investment returns are not guaranteed.
  • This is a simple estimate from your inputs and a general formula; verify officially before any real or commercial use.

Guides

How compounding works

Compound interest earns interest on interest. The longer the period, the more the principal, monthly contribution, and return rate drive the result.

Care with the return assumption

It simulates assuming the entered return holds. Taxes, fees, and market changes must be considered separately.

FAQ

Are returns guaranteed?

No. It is a simple calculation assuming the entered return holds.

How do compound and simple interest differ?

Simple interest accrues only on the principal; compound interest also accrues on previously earned interest.

Can I enter only an initial amount with no monthly contribution?

Yes. Set the monthly contribution to 0 to compound only the initial amount.

Are taxes or inflation reflected?

No. It uses nominal amounts, excluding interest income tax and inflation.

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