Compound Interest Calculator

How it works

Enter a starting principal, annual interest rate, compounding frequency, and number of years. The tool applies the compound interest formula—principal times (1 + rate ÷ periods) to the power of periods times years—to project the future value.

Benefits

• Models five common compounding frequencies
• Shows future value and total interest separately
• Calculates instantly with no page reload
• Keeps all financial figures on your device only

Use cases

• Project how savings grow over a set number of years
• Compare future value across compounding frequencies
• Estimate the impact of a higher interest rate
• Check textbook or coursework compound interest problems

Best practices

• Use the account's stated annual nominal rate, not APY, for accuracy
• Match the compounding frequency to your account's actual terms
• Remember this models a single lump sum, not recurring deposits
• Compare total interest, not just future value, across scenarios

Common mistakes

• Confusing nominal annual rate with annual percentage yield
• Assuming more frequent compounding always matters a lot
• Forgetting this excludes ongoing contributions or withdrawals
• Entering the rate as a decimal instead of a percentage

Privacy

Principal, rate, and term figures are calculated locally in your browser. Compound Interest Calculator does not upload or store your financial details on any server.