CalcSuite Pro

Compound Interest Calculator

Estimate how an investment grows over time with compound interest, monthly contributions, and varying compounding frequencies.

Quick Answer

A compound interest calculator estimates how money grows when interest compounds on the principal plus accumulated interest over time.

Compound Interest Formula

A = P(1 + r/n)^(nt) Where: A = final amount P = principal (initial investment) r = annual interest rate (as decimal, e.g., 0.07) n = number of times interest compounds per year t = time in years With contributions: FV = P(1+r/n)^(nt) + PMT × ((1+r/n)^(nt) − 1) / (r/n)

Example: $10,000 at 7% for 10 Years

Given

Principal

$10,000

Rate

7% / year

Period

10 years

Frequency

Monthly

Steps

  1. 1r = 7% / 12 = 0.5833% per month
  2. 2n × t = 12 × 10 = 120 periods
  3. 3A = 10,000 × (1 + 0.00583)^120
  4. 4A = 10,000 × 2.0097 ≈ $20,097

Result

Final balance: ~$20,097 | Interest earned: ~$10,097

How to Use This Calculator

  1. 1

    Enter your initial principal (starting amount).

  2. 2

    Enter the annual interest rate as a percentage.

  3. 3

    Enter the investment period in years.

  4. 4

    Optionally enter a monthly contribution amount.

  5. 5

    Select how frequently interest compounds (monthly is most common).

  6. 6

    Click Calculate to see final balance, interest earned, and year-by-year growth.

Frequently Asked Questions

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. The more frequently interest compounds, the faster money grows.

This calculator provides projections only and does not guarantee investment returns. Actual results vary with market conditions, fees, and taxes.

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Last updated: June 2026