Calculate simple interest, maturity value, and annual, monthly, and daily interest estimates.
USD inputs · transparent calculation assumptions
Instant updates as inputs change
Data is calculated in this browser only
USD inputs · transparent calculation assumptions
Simple interest earned$1,500.00
Maturity value
$11,500.00
Annual interest
$500.00
Monthly interest estimate
$41.67
Daily interest estimate
$1.37
Selected term
3 years
Calculation notes
Understand the Simple interest calculator
Simple interest = principal × annual rate × (whole years + additional months / 12). Maturity value adds principal. Daily interest uses annual interest divided by the selected 360–366 day basis. The calculation runs locally and keeps cash-flow timing consistent with the stated assumptions.
Formula and logic
How do I calculate simple interest over years and additional months?
Simple interest = principal × annual rate × (whole years + additional months / 12). Maturity value adds principal. Daily interest uses annual interest divided by the selected 360–366 day basis.
Worked example
What is the maturity value of $10,000 at 5% simple interest for three years?
At $10,000 principal, 5% annual simple interest, and three years, interest is $1,500 and maturity value is $11,500. Adding six months adds another $250 without compounding prior interest.
How to read the result
Does simple interest accrue on previously earned interest?
Simple interest earns interest on the original principal only.
The daily value is a reference rate; the main term uses years and months rather than actual dates.
Limits and assumptions
Does selecting a 360-day basis change the years-and-months interest total?
Day-count basis changes only the daily reference, not the years-and-months total. Does not model amortizing loans, actual dates, late fees or early withdrawals. A month is always one twelfth of a year.