Formula
Rate per year: r = I / (P · t) where t is time in years and A = P(1 + r t).
Rate per month/day shown by dividing the annual rate by 12 or 365 respectively.
Simple Interest Rate Calculator – Fast, Accurate & Free
Need to know the interest rate on a loan, savings deposit, or short-term investment? This Simple Interest Rate Calculator lets you enter your End Balance (A), Principal (P), and Term (t) to instantly compute the total interest and the simple interest rate (per year, month, or day). No math headaches—just clean results.
What is Simple Interest?
Simple interest is interest calculated only on the original principal. It grows linearly with time, making it ideal for quick estimates on short-term loans, invoices, savings products, and classroom problems.
| Loans: personal, payday, short-term business lending |
| Savings & Deposits: fixed deposits that quote flat returns |
| Education: homework, exams, and finance basics |
| Pricing & Invoices: late-fee calculations at a flat rate |
Why This Calculator Matters
- Accuracy: eliminates manual mistakes with clean formulas.
- Speed: instant results for quick decisions.
- Clarity: shows total interest and rate with adjustable units.
- Planning: compare offers and evaluate true borrowing costs.
- Education-friendly: perfect for teaching and learning finance.
How to Use the Calculator
- Enter your End Balance, Principal, and Term (choose years, months, or days).
- Click Calculate to see Total Interest and Interest Rate.
- Switch the rate view to per year, per month, or per day.
Frequently Asked Questions
Is this different from a compound interest calculator?
Yes. Simple interest does not compound; compound interest grows on both principal and previously earned interest. For compounding scenarios, use a compound interest calculator.
Can I use months or days for the term?
Absolutely. The tool converts months to years (÷12) and days to years (÷365) behind the scenes for accurate rate calculations.
What if my end balance equals the principal?
The total interest is $0 and the rate will be 0%.
Does this include fees or taxes?
No. Simple interest is a pure rate calculation. Add any fees or taxes separately if you need an all-in cost.