Simple Interest Calculator
Calculate simple interest on investments or loans.
Simple Interest Formula
I = P × R × T
📘 How It Works
Simple Interest Formula
Interest (I) = Principal (P) × Rate (R) × Time (T). Rate is expressed as a decimal (5% = 0.05), time in years.
Rate Conversion
Annual percentage rate is divided by 100 to get the decimal form. 5% becomes 0.05 for the calculation.
Total Amount
Total = Principal + Interest. This is what you'll have at the end of the period (or owe, for loans).
Time Flexibility
Fractional years work: 0.5 = 6 months, 0.25 = 3 months. Adjust time input to match your actual period.
Simple vs. Compound
Simple interest only calculates on principal. Compound interest calculates on principal + accumulated interest.
💡 Common Use Cases
Short-Term Loans
Calculate interest on payday loans or short-term borrowing where simple interest is commonly used.
Car Loans
Some auto loans use simple interest. Calculate expected interest costs before committing.
Savings Bonds
Government bonds often pay simple interest. Calculate expected returns on bond investments.
Educational Loans
Student loans often accrue simple interest during school. Understand interest accumulation before graduation.
Personal Lending
Calculate fair interest when lending to or borrowing from friends/family. Keep things transparent.
Math & Finance Education
Learn the fundamental concept of interest before moving to compound interest calculations.