What is the Simple Interest Calculator?
Simple Interest is the interest calculated only on the original principal — it does not compound. The FinanceDeck Simple Interest Calculator instantly gives you the interest amount and total maturity value for any principal, rate and tenure.
This is the model still used for many short-term loans, informal borrowing, some auto loans and certain government schemes. Understanding simple interest is also the first step to appreciating just how much more you gain (or lose) when compounding enters the picture.
How does it work?
The calculator multiplies principal by rate by time (in years) and divides by 100. That's it — no compounding, no reinvestment of interest. Enter any three of the four variables and see the result live.
Compare the same principal and rate against the Compound Interest Calculator to see how much you're leaving on the table when interest doesn't compound. Over long tenures the gap is dramatic — sometimes more than double.
SI = P × R × T / 100Example
Lend ₹1,00,000 at 8% simple interest for 5 years.
Interest works out to ₹40,000 flat. Total repayment is ₹1,40,000. Under compound interest at the same rate, the amount would grow to ₹1,46,933 — an extra ₹6,933 from compounding.
Benefits
- ✓Simple, transparent calculation
- ✓Ideal for short-term personal loans
- ✓Great teaching tool for students
- ✓See exactly what you'll owe or earn
- ✓Quick sanity check before signing informal loan papers
Frequently Asked Questions
When do banks use simple interest?
Some auto loans, some corporate bonds and many informal loans use simple interest. Most retail bank products use compound interest instead.
Is simple interest better than compound?
For a borrower, yes — you pay less. For a saver, no — you earn less. Always check which model applies to your product.
Does the tool handle fractional years?
Yes. Enter a decimal like 2.5 for two-and-a-half years.
Can I use it for daily interest?
Yes — convert days to years (e.g. 90 days = 0.2466) and enter that as T.
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