Calculate simple interest quickly by entering principal amount, interest rate, and time period.
| Period | Interest This Period | Cumulative Interest | Total Amount |
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Select whether you want to calculate the interest, total amount, principal, rate, or time period from the "Solve For" dropdown.
Type in the values you know — principal, rate, and time. Choose your time unit (years, months, or days) for flexible input.
Results appear in real time: simple interest, total amount, daily rate, monthly rate, and year-by-year breakdown — no button needed.
Copy to clipboard, download a CSV with the full schedule, or print a clean PDF report for records, homework, or financial planning.
Results update as you type — no Calculate button needed. Change any value and instantly see how it affects your interest and total amount.
Not just SI = P×R×T. Rearrange the formula to find Principal, Rate, or Time given the other values. Five calculation modes in one tool.
Enter time in years, months, or days — the calculator automatically converts to the correct fractional year for accurate results every time.
See a detailed period-by-period schedule showing interest earned each year, cumulative interest, and total amount — scroll through the full timeline.
All calculations run entirely in your browser. No data is ever sent to a server, stored, or tracked — your financial figures stay completely private.
The full applied formula with your substituted values is shown in the results panel — perfect for students who need to verify their working.
Fully responsive design works perfectly on desktop, tablet, and mobile. Calculate anywhere — in class, at the bank, or on the go.
Download results as a CSV for spreadsheets, print a clean PDF report, or copy everything to clipboard to paste wherever you need it.
Simple interest is calculated only on the original principal amount — it does not compound, meaning you never pay (or earn) interest on previously accrued interest. This makes it the most transparent and easy-to-understand form of interest.
The formula is SI = P × R × T, where P is principal, R is the annual interest rate (as a decimal), and T is time in years. The total amount repaid or received is A = P + SI.
Simple interest never compounds — you only ever pay (or earn) interest on the original principal. This makes it predictable and easy to plan around, unlike compound interest which accelerates over time.
Simple interest grows in a straight line over time. Double the time and you double the interest. This linear relationship makes mental math and quick estimates straightforward.
Because interest is calculated on the principal, paying down your balance early reduces your outstanding principal immediately — every extra payment directly cuts your interest cost.
Simple interest is standard for car loans, personal loans, and most short-term borrowing. The shorter the term, the smaller the gap between simple and compound interest costs.
If you're investing or saving, compound interest is significantly better — your interest itself earns interest. Simple interest is fairer for short-term deposits but underperforms compound growth over many years.
Many modern auto and personal loans use "daily simple interest" — interest accrues daily on the principal balance. Paying early in the month slightly reduces total interest vs. paying on the due date.
Calculate compound interest growth on savings or investments with regular contributions.
Calculate EMI for home, car, personal, and education loans all in one unified tool.
Calculate daily interest on loans, savings accounts, or investments with precise day-by-day breakdown.
Estimate your monthly mortgage EMI with down payment planning and amortization schedule.
Quickly compute your monthly car loan repayment and total interest payable.
Compute monthly EMI for personal loans across medical, wedding, travel, and general purposes.
Free, instant, and accurate no account required. Run your first calculation in under 10 seconds.
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