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Rotina Diária

Compound Interest Calculator

Estimate investment growth with monthly contributions, a monthly or annual rate, and a month-by-month table you can download as a CSV.

Simulation excludes taxes and management fees. Past or estimated returns don't guarantee future results.

Processed on your device. Nothing you type is sent anywhere.

How to use: Compound Interest Calculator

  1. Enter your starting balance and how much you plan to contribute each month.
  2. Enter the interest rate and choose whether it’s monthly or annual.
  3. Set the investment period to see your ending balance, total contributions, and total interest earned.
  4. View your month-by-month growth or download the table as a CSV file for Excel.

About this tool

With compound interest, each month’s interest earns interest in the months that follow. Over time, this effect accelerates: over longer periods, accumulated interest can exceed the amount you contributed. The formula without contributions is M = C × (1 + i)n.

An annual rate is converted to its equivalent monthly rate using (1 + annual rate)1/12 − 1, not by dividing by 12: 12% per year is about 0.949% per month. This calculation doesn’t account for taxes or fees.

Frequently asked questions

What’s the difference between simple and compound interest?

With simple interest, interest is earned only on the starting amount. With compound interest, it’s earned on the growing balance, including previously earned interest—a method used for investments and loans.

How do you convert an annual rate to a monthly rate?

Use (1 + annual rate)^(1/12) − 1. For example: 12% per year → 1.12^(1/12) − 1 ≈ 0.9489% per month. Dividing by 12 (1% per month) overestimates the return.

Does this calculation include taxes?

No. Taxes and fees vary by investment and location. Factor them in when comparing your estimated returns with those from a savings account.

Is it really free? Is there a daily limit?

It's free with no daily limits. Processing happens on your device, so there's no per-use cost and no need to limit you.

Does it work on phones?

Yes. The site works in any modern browser on Android, iPhone, Windows, Mac, and Linux—no installation needed.

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