Solve for any value
Find the interest, principal, rate or time. Just pick what you want and fill in the rest.
Solve for interest, principal, rate or time
Simple Interest CalculatorInterest, Total Amount & Rupee Rate
Use this free simple interest calculator to find the interest and total amount on any loan, deposit or private lending in seconds. You can also work backwards to the principal, rate or time, convert a monthly rupee rate to an annual rate and compare the result with compound interest.
- Solve any of 4 values
- Years, months and days
- Monthly rupee rate
- Simple vs compound chart
Simple vs compound growth
3 yrs at 8.00% a yearSimple interest balanceCompound interest (yearly)
| Year | Interest | SI balance | CI balance |
|---|---|---|---|
| 1 | ₹4,000 | ₹54,000 | ₹54,000 |
| 2 | ₹4,000 | ₹58,000 | ₹58,320 |
| 3 | ₹4,000 | ₹62,000 | ₹62,986 |
Why this tool
A Smarter Simple Interest Calculator
Most calculators only find the interest. This one solves every part of the formula and shows how your money moves over time.
Exact time periods
Enter years, months and days together, so short loans and odd periods are calculated correctly.
Monthly rupee rate
Enter a rate like ₹2 per ₹100 per month and see the true yearly rate behind it.
Simple vs compound chart
An interactive chart compares both methods, so you see how the gap widens over time.
Year-by-year schedule
A clear table lists the interest and balance for every year, or every month for short periods.
Private and instant
All maths runs in your browser. Nothing is saved or sent, and there is nothing to sign up for.
How to use
How to Calculate Simple Interest Online
The result updates as you type, so you can test different numbers instantly.
Choose what to find
Select interest, principal, rate or time. The form shows only the fields you need.
Enter the principal
Type the amount borrowed or invested, or drag the slider.
Add the interest rate
Enter the rate and pick per year or per month. Monthly rupee rates are converted for you.
Set the time period
Fill in years, months and days, or tap a preset for common periods.
Read and compare
Check the interest, total amount and compound comparison. Then copy the result to share it.
The formula
Simple Interest Formula
Simple interest is charged only on the original principal. Unlike compound interest, earlier interest never earns more interest, so the amount grows in a straight line.
To find it, multiply the principal by the yearly rate and the time in years, then divide by 100. After that, add the interest to the principal to get the total amount.
Worked example
Suppose you lend ₹50,000 at 8% a year for 3 years. The simple interest is ₹50,000 × 8 × 3 ÷ 100 = ₹12,000. So the borrower repays ₹62,000 in total. With yearly compounding, the same money would grow to about ₹62,986.
Months and days
For periods shorter than a year, convert time into years first. For example, 9 months is 0.75 years and 90 days is about 0.25 years.
Simple interest formulas
SI = P × R × T ÷ 100
- Total amount: A = P + SI
- Principal: P = SI × 100 ÷ (R × T)
- Rate: R = SI × 100 ÷ (P × T)
- Time: T = SI × 100 ÷ (P × R)
- Units: R is the yearly rate in %, and T is the time in years.
| ₹1,00,000 for 5 years | Simple interest | Compound (yearly) |
|---|---|---|
| At 6% | ₹30,000 | ₹33,823 |
| At 8% | ₹40,000 | ₹46,933 |
| At 10% | ₹50,000 | ₹61,051 |
| At 12% | ₹60,000 | ₹76,234 |
Rupee rate
Monthly Rupee Rate to Yearly Interest Rate
Private lenders and gold loans in India often quote interest as rupees per ₹100 per month. Multiply that figure by 12 to get the yearly rate used in the simple interest formula.
| Quoted rate | Yearly rate | Interest on ₹1 lakh for 1 year |
|---|---|---|
| ₹1 per ₹100 per month | 12% a year | ₹12,000 |
| ₹1.5 per ₹100 per month | 18% a year | ₹18,000 |
| ₹2 per ₹100 per month | 24% a year | ₹24,000 |
| ₹3 per ₹100 per month | 36% a year | ₹36,000 |
Watch out: a rate that sounds small per month can be very high per year. Always compare lenders on the yearly rate.
Compare
Simple Interest vs Compound Interest
Both start from the same principal and rate. The difference is whether interest is added to the balance before the next period.
| Feature | Simple interest | Compound interest |
|---|---|---|
| Charged on | Original principal only | Principal plus earlier interest |
| Growth | Straight line | Faster, curved growth |
| Common uses | Car loans, short personal loans, private lending, some bonds | Bank deposits, savings, mutual funds, credit cards |
| Better for | Borrowers | Savers and investors |
| Plan it with | This simple interest calculator | Compound interest calculator |
Benefits
Benefits of Using This Calculator
- Check a lender's quote before you borrow.
- Settle interest on money lent to friends or family fairly.
- Find how long it takes for money to double.
- Verify homework and exam answers with the working shown.
- See the real yearly cost of a monthly rupee rate.
- Compare simple and compound returns side by side.
FAQ
Simple Interest Calculator FAQs
Quick answers to the most common simple interest questions.
What is simple interest?
Simple interest is interest charged only on the original principal, not on interest already earned. It grows by the same amount every year, so the total rises in a straight line.
How do you calculate simple interest?
Multiply the principal by the yearly interest rate and the time in years, then divide by 100. For example, ₹50,000 at 8% for 3 years gives ₹50,000 × 8 × 3 ÷ 100 = ₹12,000.
How do I calculate simple interest for months or days?
Convert the time into years first. Divide months by 12 and days by 365, then use the normal formula. This calculator does the conversion when you enter years, months and days together.
What does ₹2 per ₹100 per month mean?
It means you pay ₹2 of interest every month for each ₹100 borrowed. That equals 24% a year, or ₹2,000 a month on a loan of ₹1 lakh. Select Per month in the calculator to convert any rupee rate.
How long does it take to double money at simple interest?
Divide 100 by the yearly rate. At 8% simple interest, money doubles in 12.5 years, and at 10% it doubles in 10 years. Choose Time in the calculator and enter interest equal to the principal to check any rate.
Is simple interest better than compound interest?
Simple interest is better when you borrow, because you pay less over time. Compound interest is better when you save or invest, because your returns earn returns.
Which loans use simple interest?
Simple interest is common in private lending, some gold loans, short-term personal loans and flat-rate vehicle loans. Most bank home and personal loans charge interest on the reducing balance instead, so check your loan terms.
Can I find the interest rate if I know the interest?
Yes. Choose Rate, then enter the principal, the interest paid and the time. The calculator shows the yearly rate and the equivalent monthly rupee rate.
Know the True Cost of Every Loan
Whether you are lending, borrowing or studying, a quick check saves money and mistakes. Use the simple interest calculator to see the real numbers before you agree to any deal.
Calculate simple interestMore interest and loan calculators
This simple interest calculator gives estimates for general information. Actual loan or deposit terms may use different day counts, fees or compounding, so confirm the final figures with your lender or bank.