Free Interest Calculator Online
Calculate simple or compound interest with detailed yearly breakdowns
| Year | Start Balance | Interest Earned | End Balance |
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Comprehensive Interest Analysis
Simple and compound interest with full transparency
Switch between simple interest for basic calculations and compound interest for savings, investments, and loan analysis.
Choose annually, semi-annually, quarterly, monthly, or daily compounding to match your specific financial product.
View a detailed table showing how your balance and interest grow each year over the full term.
About This Tool
This calculator computes both simple and compound interest. Simple interest is charged only on the original principal, while compound interest is charged on the principal plus all previously accumulated interest, which is why compounding grows a balance faster over time.
The frequency of compounding matters: interest added monthly grows faster than the same annual rate compounded once a year, because each period's interest starts earning sooner. The tool lets you set the rate, the period, and the compounding frequency so you can see the gap between simple and compound outcomes for the same headline rate.
The gap between simple and compound interest widens the longer money is left to grow, and more frequent compounding accelerates it further. Seeing the two side by side makes the effect concrete, which is why compounding is described as working for you when you save and against you when you borrow.
How to Use It
- Enter the principal, annual rate, and time period.
- Choose simple interest or a compounding frequency.
- Read the interest earned and the final balance.