What is the formula for simple interest?
The formula is I = P × r × t, where I = Total Interest, P = Principal, r = Annual Interest Rate (decimal), and t = Time (years).
Tool Categories
Simple Interest Calculator - Loan Tables | 1ClickTools
Calculate simple interest on loans or investments using I = P * r * t. Instant principal, rate, and time formulas with downloadable tables.
About This Tool
Simple interest is used extensively in short-term personal loans, car loans, auto financing, and commercial debt agreements. Because interest does not compound, your monthly interest charge remains static over the loan term, making calculations straightforward and predictable. The fundamental formula for simple interest is I = P × r × t, where I is total interest earned or owed, P is the starting principal, r is the annual rate of interest as a decimal, and t is the time duration in years. Understanding the difference between simple interest and compound interest is critical when evaluating loan offers or high-yield savings options. Borrowers benefit from simple interest loans because total interest cost is lower than compounding debt, while savers benefit from compound accounts because interest accrues exponentially.
Frequently Asked Questions
What is the main difference between simple and compound interest?
Simple interest is calculated only on the initial principal. Compound interest is calculated on the principal PLUS all interest accumulated from previous periods.
Where is simple interest commonly used in the real world?
Simple interest is frequently used in auto loans, short-term personal loans, bond coupon payments, and private promissory notes.
How do I calculate simple interest for months instead of years?
Divide the number of months by 12 (e.g. 6 months = 0.5 years) and plug that decimal into time (t).
Does simple interest change if I pay off early?
In simple interest loans, paying off principal early reduces total interest paid because interest is calculated daily or monthly on remaining principal.
Can simple interest be used for savings accounts?
Most modern bank savings accounts use compound interest (APY). However, fixed short-term bonds or treasury bills often pay simple interest.
What is the APR in a simple interest loan?
In a simple interest loan without extra lender fees, the annual percentage rate (APR) equals the nominal interest rate.
How do I calculate daily simple interest?
Daily simple interest = Principal × (Annual Rate / 365) × Number of Days.
Is this simple interest calculator free for business use?
Yes, 1ClickTools provides 100% free access for both personal and commercial financial planning.
Is my loan information saved on any server?
No. All calculations run strictly in client-side JavaScript inside your browser.