Simple Interest Calculator โ Linear Growth & Non-Compounding Loans
The Simple Interest Calculator calculates interest calculated strictly on the original principal amount over time. Unlike compound interest, simple interest does not add accrued interest back into the principal base; growth remains completely linear from day one to the maturity date.
1. The Mathematical Formula
I = P ร r ร tTotal Amount (A) = P + I = P ร (1 + r ร t)Where:
โข P: Principal sum borrowed or invested.
โข r: Annual interest rate expressed as a decimal (e.g. 6% = 0.06).
โข t: Time period in years (convert months by dividing by 12, or days by 365).
2. Simple Interest vs. Compound Interest
| Feature | Simple Interest | Compound Interest |
|---|---|---|
| Growth Pattern | Linear (equal interest earned every year) | Exponential (interest earns interest) |
| Principal Base | Stays constant over the entire tenure | Increases at each compounding frequency (monthly, quarterly, annually) |
| Typical Usage | Short-term debt, promissory notes, auto loans (certain simple-interest contracts) | Savings accounts, FDs, PPF, mutual funds, mortgages, credit cards |
3. Where Simple Interest Is Applied
Simple interest is predominantly encountered in informal promissory loans between individuals, short-term commercial paper, dealer vehicle loans that calculate interest on daily reducing balances without reinvestment, and statutory court judgments for delayed payments.
For compounding instruments, switch to our Compound Interest Calculator or our Interest Calculator which supports side-by-side mode switching.
4. Step-by-Step Calculation Example
Scenario: Principal = โน1,00,000, Annual Rate = 7.5%, Time = 4 years.
โข Interest = โน1,00,000 ร 0.075 ร 4 = โน30,000.
โข Total Amount = โน1,00,000 + โน30,000 = โน1,30,000.
โข Annual Interest Earned = โน7,500 every single year (constant).
โข Interest = โน1,00,000 ร 0.075 ร 4 = โน30,000.
โข Total Amount = โน1,00,000 + โน30,000 = โน1,30,000.
โข Annual Interest Earned = โน7,500 every single year (constant).
