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Home / Calculators / Interest Calculator

Free Interest Calculator

Calculate simple and compound interest easily for any investment or loan. Track growth over time with an interactive chart.

initial amount ($)
percentage (%)
years
extra per month ($)
Please enter valid values.
Interest Results
$0.00
Final Amount
$0.00
Total Interest
$0.00
Total Contributions
0.00%
Effective Annual Rate
Growth Over Time

How to Use the Interest Calculator

1

Select Interest Type

Choose between Simple or Compound interest. Compound interest grows faster and is used by most savings and investment products.

2

Enter Your Details

Enter the principal amount, annual interest rate, time period, and for compound interest choose the compounding frequency and optional monthly additions.

3

View Results

Click "Calculate" to see the final amount, total interest earned, effective annual rate, and a year-by-year growth chart.

About Interest Calculators

An Interest Calculator helps you compute the growth of your money over time using either simple or compound interest. Simple interest is calculated only on the principal amount using the formula A = P(1 + rt). Compound interest is calculated on both the principal and accumulated interest using the formula A = P(1 + r/n)nt, which means your money grows exponentially over time.

The compounding frequency plays a key role in your returns. More frequent compounding (daily, monthly) results in higher total interest earned because interest is added to your principal more often, allowing you to earn interest on interest. Monthly additions can also significantly accelerate your savings growth.

This calculator works for any interest-bearing scenario: savings accounts, investment returns, certificates of deposit (CDs), bonds, and simple-interest loans. For loan-specific calculations with amortization schedules, try our Loan Calculator or Mortgage Calculator.

  • Simple Interest: Interest is calculated only on the original principal. Linear growth.
  • Compound Interest: Interest is calculated on principal + accumulated interest. Exponential growth.
  • Rule of 72: Divide 72 by your annual rate to estimate years to double your money.

Frequently Asked Questions

Simple interest is calculated only on the principal amount using the formula A = P(1 + rt). Compound interest is calculated on both the principal and accumulated interest using the formula A = P(1 + r/n)^(nt), which means your money grows faster over time because you earn interest on your interest.

Select either Simple or Compound interest, enter the principal amount, annual interest rate, time period, and for compound interest choose the compounding frequency (daily, monthly, quarterly, semi-annually, or annually). Click Calculate to see the total amount, total interest earned, and a year-by-year growth chart.

Yes, it is completely free. No registration, downloads, or payments are required. You can use it unlimited times for personal, educational, or professional financial planning.

No. All calculations happen locally in your browser. Your principal, rate, and other financial data never leave your device. We do not store, track, or have access to any information you enter.

Compounding frequency refers to how often interest is calculated and added to your principal. Common frequencies are daily, monthly, quarterly, semi-annually, and annually. More frequent compounding results in higher total returns because interest is added to your principal more often, allowing you to earn interest on interest more frequently.

The compound interest calculator uses the formula A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual interest rate (as a decimal), n is the number of compounding periods per year, and t is the time in years.

Yes, this calculator works for any scenario involving interest: savings accounts, investment returns, certificates of deposit (CDs), bonds, and loans. For savings and investments use compound interest, for simple-interest loans use the simple interest mode.

The Rule of 72 is a simple way to estimate how long it takes an investment to double. Divide 72 by your annual interest rate to get the approximate number of years. For example, at 8% interest, your money will double in about 72 / 8 = 9 years.

Absolutely. The tool is fully responsive and works seamlessly on all devices including smartphones, tablets, laptops, and desktops. The layout automatically adjusts to your screen size.