Simple Interest Calculator
Solve any variable in the classic simple interest formula $I = P \cdot r \cdot t$. Seamlessly compare banker\'s rules vs exact 365-day conventions.
Maturity Value (P + I): $10,250
Parameters
Understanding the Simple Interest Equations
Simple interest is a quick and easy method of calculating interest charge on a loan or investment. It is determined by multiplying the daily interest rate by the principal by the number of days that elapse between payments.
The Four Variables of Simple Interest
Our calculator functions as a Four-Variable Algebraic Solver. This means if you input any three of the variables, the calculator solves for the fourth:
- Interest Amount ($I$): Calculated as $I = P \cdot r \cdot t$. This is the raw dollar profit or charge.
- Principal ($P$): The starting capital sum borrowed or lent. Solved as $P = I / (r \cdot t)$.
- Annual Interest Rate ($r$): The nominal yearly yield. Solved as $r = I / (P \cdot t)$.
- Time Term ($t$): The length of the loan/investment in years. Solved as $t = I / (P \cdot r)$.
Ordinary Interest (Banker's Rule) vs. Exact Interest
When counting time in days, financial institutions use two primary methods:
- Ordinary Interest (360-day base): Assumes a year has exactly 360 days. This makes manual division uniform and is widely utilized in commercial finance. Because it divides by a smaller denominator, it results in slightly larger interest payments.
- Exact Interest (365-day base): Uses the actual 365 days of the calendar year (or 366 in leap years) for maximum literal mathematical accuracy.
How Simple Interest Calculator Works
Our high-performance online utility runs entirely client-side, processing your requests securely and instantly inside your web browser. For related features, you can also use our Interest Calculator and Finance Calculators tools.
Enter Known Values
Provide your parameters or upload your file securely into the workspace.
Choose Day Count
Our 100% offline-first engine processes the request instantly in browser memory.
Solve for Missing Variable
Download, copy, or print the optimized results instantly with complete privacy.
Interest Calculation Methods
Designed for professional results, privacy, and maximum compatibility across all modern desktop and mobile browsers. Enjoy unlimited free calculations without hidden fees.
Frequently Asked Questions About Simple Interest
Is this simple interest calculator free?
Yes. Calculate unlimited simple interest with no registration.
What's the formula for simple interest?
I = P × r × t. Calculate Interest from Principal, Rate, and Time.
Does this support Banker's Rule?
Yes. Choose between 360-day Banker's Rule and exact 365-day calculations.
Do you store financial data here?
No. All calculations run locally with complete privacy.