iHow it is calculated
Simple interest is calculated only on the initial principal, without reinvesting the gain:
interest = principal × rate × time
At 10,000, 5% a year, over 3 years: interest = 10,000 × 0.05 × 3 = 1,500, so total 11,500.
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Finance · Updated 2026
Simple Interest Calculator
Calculate simple interest and the total amount from principal, annual rate and period, with the classic P × r × t formula.
Enter your data
RON
%
yrs
Simple interest is calculated only on the initial amount, without reinvesting the gain.
=Final total
11,500RON
Amount (principal)10,000 RON
Interest+1,500 RON
Final total11,500 RON
10,000 × 5% × 3 = 1,500 RON
Interest = 1,500 RON · Final total 11,500 RONStandard financial formulas (time value of money). Instant in-browser calculation, no account, no data sent. Interest rates are indicative — check the bank’s actual offer.
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?Frequently asked questions
What is simple interest?
It is interest calculated only on the initial amount (the principal), for the whole period. Unlike compound interest, the gain is not added to the capital.
How is simple interest calculated?
Interest = principal × rate × time. For example, 10,000 at 5% over 3 years = 10,000 × 0.05 × 3 = 1,500 interest, so 11,500 in total.
When is simple interest used?
On some short-term loans, fixed-coupon bonds and quick estimates. Most bank deposits and loans, however, use compound interest.
What is the difference from compound interest?
With simple interest the gain is the same each year. With compound interest, interest is reinvested and grows, so over long periods the result is larger.
How do I calculate interest over months or days?
Convert the period into years: divide months by 12, days by 365. For example, 6 months = 0.5 years in the formula.
Is simple interest taxed?
In Romania, interest income is taxed at 10%. The calculator shows gross interest; for the net figure, subtract the applicable tax.
What is the annual rate?
It is interest expressed as a percentage of the principal per year. At 5% a year, every 100 earns 5 in simple interest over one year.
Can I use this for a loan between individuals?
Yes, it is useful for simple fixed-rate loans. Agree clearly on the principal, rate and period, and the total interest follows directly from the formula.
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