Simple Interest Calculator
Calculate simple interest earned and final balance on principal.
Calculator InputsInstant Math
Results & Calculation SummaryVerified
Final Accumulated Balance
$1,100.00
With a principal of $1,000.00, an annual interest rate of 5%, and a duration of 2 years, the simple interest earned is $100.00, giving a total final balance of $1,100.00.
Total Interest Earned
$100.00
Original Principal
$1,000.00
What is Simple Interest Calculator and How is it Calculated?
The CalcTower Simple Interest Calculator determines the exact interest earned and total final balance on a principal amount over time. Simple interest is calculated solely on the original principal without compounding.
I = 1000 * 0.05 * 2 = $100 total interest earned.
Time converted to 0.5 years (6/12): 5000 * 0.06 * 0.5 = $150.
Common Real-World Use Cases
Many short-term consumer loans charge simple interest rather than compound - use this to see the exact interest cost before signing.
Check the total repayment amount on a private loan or IOU that specifies a flat annual interest rate.
Verify that a lender’s stated interest figure matches the standard I = P × R × T calculation before agreeing to terms.
How This Compares
Simple interest is calculated only once, on the original principal, for the whole term. Compound interest recalculates interest on the growing balance at each compounding period, so it earns "interest on interest." For the same rate and term, compound interest always produces a larger total than simple interest - use the Compound Interest Calculator if your loan or investment compounds.
- 1Enter the starting Principal Amount (e.g. $1,000).
- 2Enter the annual Interest Rate percentage (e.g. 5%).
- 3Enter the Time duration and choose the unit (Years, Months, or Days).
- 4View total interest earned and accumulated final balance instantly.
- •Simple interest is commonly used for short-term personal loans, car financing, and simple bonds.
- •Unlike compound interest, simple interest does not earn interest on previous interest.
- •Assuming the loan uses simple interest when it actually compounds - check the loan agreement, since compounding produces a higher total cost than this calculator models.
- •Entering a monthly rate instead of the annual rate - this calculator expects the annual percentage rate; a rate already stated "per month" needs multiplying by 12 first.
Results are estimates for informational and educational purposes and may differ from actual lender, bank, tax, or investment results.
Frequently Asked Questions
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