Simple Interest Calculator
Simple interest computes linear interest charges strictly on the original principal balance without compounding prior interest periods, governed by I = P × (r / 100) × t.
Total linear interest earned or owed over the term
Original principal lent or invested
Flat annual percentage rate
Loan or note duration in years
Step-by-Step Calculation
Simple interest computes linear interest charges strictly on the original principal balance without compounding prior interest periods, governed by I = P × (r / 100) × t.
Real-World Reference Values
Typically quoted on a simple day-count basis
Flat annual interest over 6 to 24 months
State-mandated simple accrual rate
20-Row Comparison Table
Simple Interest Accrued (I) · Principal Amount (P)
| # | Principal Amount ($) | Simple Interest Accrued ($) | Δ % |
|---|---|---|---|
| 01 | 100 $ | 18 $ | -99.00% |
| 02 | 10,000.00 $Current | 1,800.00 $ | 0.00% |
| 03 | 15,614.34 $ | 2,810.58 $ | +56.14% |
| 04 | 23,371.51 $ | 4,206.87 $ | +133.72% |
| 05 | 31,128.68 $ | 5,603.16 $ | +211.29% |
| 06 | 38,885.86 $ | 6,999.45 $ | +288.86% |
| 07 | 46,643.03 $ | 8,395.74 $ | +366.43% |
| 08 | 54,400.20 $ | 9,792.04 $ | +444.00% |
| 09 | 62,157.37 $ | 11,188.33 $ | +521.57% |
| 10 | 69,914.54 $ | 12,584.62 $ | +599.15% |
| 11 | 77,671.71 $ | 13,980.91 $ | +676.72% |
| 12 | 85,428.88 $ | 15,377.20 $ | +754.29% |
| 13 | 93,186.05 $ | 16,773.49 $ | +831.86% |
| 14 | 100,943.22 $ | 18,169.78 $ | +909.43% |
| 15 | 108,700.39 $ | 19,566.07 $ | +987.00% |
| 16 | 116,457.57 $ | 20,962.36 $ | +1064.58% |
| 17 | 124,214.74 $ | 22,358.65 $ | +1142.15% |
| 18 | 131,971.91 $ | 23,754.94 $ | +1219.72% |
| 19 | 139,729.08 $ | 25,151.23 $ | +1297.29% |
| 20 | 147,486.25 $ | 26,547.52 $ | +1374.86% |
Frequently Asked Questions
When is simple interest used instead of compound interest?+
Simple interest is standard for short-term commercial paper, Treasury bills, bridge notes, and certain auto or consumer installment contracts.
How do I find total repayment with simple interest?+
Add the solved interest I directly to the principal P: Total = P + I.
Can I enter months instead of years for t?+
Yes. Switch the inline unit selector on t from Years (yr) to Months (mo) and the solver automatically scales by 1/12.