Simple Interest Calculator
No compounding — just principal, annual rate, and time in years. Click any i for detail.
Loan or note
Principal ($)
i
Principal
Starting amount. |
|
|---|---|
Annual rate (%)
i
Rate
Simple annual interest rate. |
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Time (years)
i
Time
Can be a fraction (6 months = 0.5). |
How to use this calculator
- Enter principal.
- Enter the annual simple rate.
- Enter years (use 0.5 for six months).
- Compare with compound interest if interest is added to the balance.
Results explained
I = P × (rate/100) × years. Total payback = P + I. Amortizing car and student loans use compound/amortizing math instead.
Quick reference: simple vs compound
Credit cards and most installment loans are not simple interest in this textbook sense.
| Item | Detail |
|---|---|
| $10k @ 6% for 1 yr | $600 interest |
| Same, 6 months | $300 |
| Compound monthly | See compound interest |
| Amortizing P&I | Car / personal loan pages |
Some discount notes quote simple interest and withhold it up front — that is a different structure.
How the estimate is built
I = P r t, r as a decimal, t in years. Total = P + I.
Example scenario
$10,000 at 6% for 3 years → $1,800 interest, $11,800 payback.
FAQ
Bank account APY?
That is compound — use compound interest or CD pages.
Daily simple interest auto loans?
Real auto interest is usually daily simple on declining balance — closer to amortizing than I=Prt on the original P.
Months only?
Years = months ÷ 12.