Interest Calculator
Calculate simple or compound interest with optional monthly contributions.
Enter your values to see the result.
Results are estimates for planning only. Actual figures depend on your lender or bank, fees, rounding and the exact dates used, so confirm the numbers before you sign anything.
Continue your work
- Fixed Deposit (STDR) Calculator — Calculate a compounding fixed deposit.
- Rule of 72 Calculator — Estimate how quickly money doubles.
Rate this tool
0.0
0 ratings
- 5 stars 0
- 4 stars 0
- 3 stars 0
- 2 stars 0
- 1 star 0
Share this tool
Found it useful? Send it to a friend or teammate.
Report an issue
Something broken or not quite right? Tell us and we will look into it.
Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
No sign-up required. Tool-specific limits may apply.
How to use the Interest Calculator
The interest calculator shows how money grows with simple or compound interest. Choose how often interest compounds, add an optional monthly contribution, and see the final balance, total interest, effective annual rate and a year-by-year table. It is useful for savings accounts, deposits, investments and understanding how interest builds on a loan.
- 1 Enter the starting amount, the annual interest rate and the number of years.
- 2 Choose simple interest or a compounding frequency, and add a monthly contribution if you plan to keep saving.
- 3 Read the final balance, the interest earned and the yearly breakdown.
Example and practical tips
$10,000 at 6% compounded monthly grows to about $18,194 after 10 years. With simple interest it would grow to only $16,000, because compound interest also earns interest on past interest.
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is paid only on the original amount. Compound interest is added to the balance and then earns interest itself, so balances grow faster over time.
Does compounding frequency matter much?
More frequent compounding slightly increases growth. At 6%, monthly compounding gives an effective rate of about 6.17% a year versus 6% for yearly compounding.
What is the effective annual rate?
It is the yearly return after compounding is included. It lets you compare accounts that compound at different frequencies.