Simple Interest Calculator
Calculate simple interest and maturity amount from principal, annual interest rate and time period — with a full breakdown and downloadable report.
Inputs
Report details (optional — appears on the PDF report)
Results
Formula
- P = principal amount · R = annual interest rate (%)
- T = time in years (months / 12, days / 365)
- A = maturity amount (principal + interest)
How It Works
Simple interest is charged only on the original principal — never on accumulated interest. So the interest earned each year is exactly the same, and the total grows in a straight line.
Time is converted to years before applying the formula: months are divided by 12 and days by 365.
Worked Example
Given: P = ₹100,000, R = 8% p.a., T = 5 years
SI = 100,000 × 8 × 5 / 100 = ₹40,000
Maturity amount A = 100,000 + 40,000 = ₹140,000
Interest per year = 40,000 / 5 = ₹8,000
Engineering Notes
- Simple interest is used for short-term loans, some vehicle and personal loans, and certain fixed deposits.
- For the same rate and period, compound interest always yields more than simple interest.
- Day-count here uses 365 days per year; some institutions use 360 or actual/actual conventions.
- Taxes (e.g. TDS on interest income) and fees are not included.
FAQ
Simple vs compound interest?
Simple interest applies only to the principal; compound interest applies to principal plus accumulated interest.
Where is simple interest used?
Short-term loans, some auto loans, discounting instruments and certain deposit schemes.
Can I enter months or days?
Yes — choose the unit and the calculator converts it to years automatically.
Related Calculators
This calculator uses established formulas and standard calculation methods to provide reliable results for planning, estimation and reference.