Free Interest Calculator Online
Calculate simple interest, compound interest, future value, savings growth, investment returns, total contributions, and interest earned with a live pie chart.
📈 Interest Calculator
Live Interest EstimateInterest Inputs
Left SideInterest Results
Right SideInterest Breakdown Pie Chart
| Year | Start Balance | Contributions | Interest | End Balance |
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Interest is calculated only on the starting principal amount.
Interest earns more interest over time, which can increase growth.
Regular deposits can strongly increase the final value over long periods.
What Is an Interest Calculator?
An interest calculator helps estimate how money can grow or how much interest may be charged over time. You can calculate simple interest, compound interest, savings growth, investment returns, future value, loan interest, and total earnings by entering a starting amount, interest rate, time period, compounding frequency, and optional monthly contributions.
This free online interest calculator is useful for savings accounts, investment planning, personal finance, loan estimates, retirement planning, and comparing how different interest rates or compounding schedules affect long-term growth.
Simple Interest Calculator
Estimate interest based only on the starting principal amount.
Compound Interest Calculator
Calculate growth when earned interest is added back to the balance.
Savings Growth Calculator
Add monthly contributions to estimate future savings and investment value.
Effective Annual Rate
Review the effective annual rate based on compounding frequency.
Simple vs Compound Interest
Simple interest calculates interest only on the original principal. Compound interest calculates interest on the principal plus previously earned interest. Over longer time periods, compounding can create much larger growth.
How Compound Interest Works
Compound interest works by adding earned interest back into the balance. The next interest calculation uses this larger balance. The more often interest compounds, and the longer the money stays invested or saved, the more powerful compounding can become.
Interest Formula Explained
This formula calculates compound interest with periodic compounding. For simple interest, the formula is I = P × r × t.
Savings Growth Examples
A small starting amount can grow steadily when interest compounds over several years.
Compare monthly and yearly compounding to see how frequency changes the final value.
Adding regular contributions can create much larger savings growth over time.
Benefits of Compound Interest
Compounding can increase savings and investment returns over longer periods.
Compare interest rates, time periods, and deposit amounts before making decisions.
Estimate future value for savings goals, investments, or financial planning.
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Frequently Asked Questions
What is compound interest?
Compound interest is interest earned on both the original principal and previously earned interest.
What is simple interest?
Simple interest is calculated only on the original principal amount.
Which earns more, simple or compound interest?
Compound interest usually earns more over time because interest is added back to the balance.
How often should interest compound?
More frequent compounding can increase growth, but rate, time, and contributions usually matter most.
Can I calculate savings growth?
Yes. Enter your starting amount, interest rate, time period, and monthly contribution.
Can I include monthly deposits?
Yes. Use the monthly contribution field to include regular deposits.
How accurate is this calculator?
It provides an estimate based on the values you enter. Actual returns may vary due to fees, taxes, market changes, or account rules.
What is APY?
APY means annual percentage yield. It reflects the annual return after compounding.
What is effective annual rate?
The effective annual rate shows the annualized return after considering compounding frequency.
Can I use it for investments?
Yes, but investment returns are not guaranteed. This tool is best for estimates and planning.