Simple Interest Calculator
Calculate simple interest
Calculate the interest and final amount of a principal with simple interest, where interest is not reinvested. Useful for short-term deposits, private loans or coursework: you need the principal, the annual rate and the term in years.
Calculate simple interest
Result
Final amount
€11,500.00
- Interest earned
- €1,500.00
Formula version: 1.0.0
How to use the simple interest calculator
- Enter the initial principal.
- Enter the annual interest rate and the term in years (decimals allowed, e.g. 1.5).
- Review the interest earned and the final amount.
Simple interest formula
I = P × r × t · Final amount = P + I
What each variable means
- I
- interest
- P
- initial principal
- r
- annual rate as a decimal
- t
- time in years
Because interest doesn't earn interest, it grows in a straight line: the same amount is added every year.
Simple interest example
€10,000 at 5% a year for 3 years earns 10,000 × 0.05 × 3 = €1,500 of interest: the final amount is €11,500.
Illustrative example with the data shown; not a guaranteed outcome.
Assumptions and limitations
- Interest is not reinvested: it is always calculated on the initial principal.
- Taxes and fees are not included.
Frequently asked questions
When is simple interest used?
In short-term deals or when interest is paid out regularly instead of being reinvested.
Which pays more, simple or compound?
At the same rate and a term longer than one period, compound interest pays more because interest also earns interest.
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See savings calculatorsIndicative result for information only; not financial or tax advice. Read the legal notice · How we calculate results
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