Simple Interest Calculator

What is simple interest?

Simple interest is interest calculated only on the original amount – the principal – for the whole period. It never earns interest on interest. If you lend ₹1,00,000 at 8% simple interest, you earn ₹8,000 every year, no matter how many years pass. That makes simple interest easy to work out and easy to check, which is why it is used for short-term loans, many car and personal loan "flat rate" quotes, private lending between people, some bonds and school maths problems.

What is a simple interest calculator?

A simple interest calculator is a free online tool that works out the interest and the total amount for you. This one handles every common case in India and elsewhere:

• Time in years, months or days.
• Interest between two dates – a simple interest calculator from date to date that counts the exact days for you.
• Rate per year or per month, such as the local "₹1 or ₹2 per hundred per month" style of lending.

It also shows interest per month and per day and a year-wise table of how the amount grows.

How to use the simple interest calculator

1. Enter the principal – the amount lent, borrowed or deposited, in rupees or any currency.
2. Enter the rate of interest and choose whether it is per year or per month.
3. Choose how you want to give the time: years, months, days or two dates.
4. Read the simple interest and total amount. The result updates as you type.

Simple interest formula

SI = (P × R × T) ÷ 100

Amount A = P + SI = P × (1 + R × T ÷ 100)

• P = principal
• R = rate of interest per year, in %
• T = time in years

Rearranging the same formula lets you find any missing value: P = 100 × SI ÷ (R × T), R = 100 × SI ÷ (P × T) and T = 100 × SI ÷ (P × R).

How to calculate simple interest with example

Simple interest for years

₹1,00,000 at 8% per year for 3 years: SI = 1,00,000 × 8 × 3 ÷ 100 = ₹24,000. The total amount is ₹1,24,000.

How to calculate simple interest in months

Convert months to years by dividing by 12. ₹50,000 at 10% for 9 months: T = 9 ÷ 12 = 0.75, so SI = 50,000 × 10 × 0.75 ÷ 100 = ₹3,750.

How to calculate simple interest for days

Divide the number of days by 365. ₹2,00,000 at 7% for 90 days: SI = 2,00,000 × 7 × 90 ÷ (100 × 365) = ₹3,452. Banks in India use 365 days for rupee deposits and loans; some other markets use 360, which gives a slightly higher figure.

Simple interest between two dates

Pick a start and end date and the calculator counts the days. From 1 January 2026 to 1 July 2026 is 181 days, so ₹1,00,000 at 12% earns ₹5,951.

Interest rate per month

In many parts of India, private loans are quoted as "₹2 per hundred per month" (do rupaye saikda). That means 2% per month, or 24% per year simple interest. On ₹50,000 for 10 months, interest = 50,000 × 2 × 10 ÷ 100 = ₹10,000. Choose "per month" in the calculator to do this directly.

Simple interest vs compound interest

With compound interest, interest is added to the principal and then earns interest itself. Over one year with yearly compounding the two are equal, but the gap grows fast after that:

Savers want compound interest; borrowers are better off with simple interest on a reducing balance. To see compounding at work, try the compound interest calculator. Fixed deposits in India compound quarterly, so use the FD calculator for them.

Simple interest on loans and EMI

A loan quoted at a "flat" rate uses simple interest on the full principal for the whole tenure: EMI = (P + P × R × T ÷ 100) ÷ number of months. ₹1,00,000 at 10% flat for 2 years gives interest of ₹20,000 and an EMI of ₹5,000. Most bank loans instead charge interest on the reducing balance, which is fairer: the same loan at a 10% reducing rate has an EMI of ₹4,614 and interest of only ₹10,748. Always compare loans on the reducing rate with the EMI calculator or the loan calculator.

Where simple interest is used

• Short-term personal and business loans, and money lent between friends and family.
• Interest on late payments, court judgments and tax refunds or dues (for example interest under the Income-tax Act is simple interest per month).
• Treasury bills and some bonds that pay a fixed coupon without reinvestment.
• Pre-EMI interest on under-construction home loans.

Simple interest in Excel

With principal in A2, rate in B2 and years in C2, use =A2*B2*C2/100 for interest and =A2+A2*B2*C2/100 for the amount. For dates, use =A2*B2/100*(D2-C2)/365 where C2 and D2 hold the start and end dates.

Dates, days or months: what to enter

• Between two dates – choose "between two dates" and enter the start and end date; the simple interest calculator counts the days in the date range for you.
• Number of days – choose "days" for a short deposit or loan; the tool also shows the interest per day.
• Months – choose "months" for a tenure in months. In the simple interest calculator the monthly formula is SI = P × R × months ÷ 1200, and the result also shows interest per month.
• Years and months – convert to months (2 years 6 months = 30 months) or to years (2.5).
• Year by year – the year-wise table shows the interest added each year.
• Rupees (INR) by default – amounts in the simple interest calculator are in Indian rupees (INR); switch the currency at the top if you need another.
• Free and online – it runs in your browser, so there is no app to install.

Simple interest calculator half yearly and quarterly

If interest is paid out half-yearly or quarterly instead of being added to the principal, it is still simple interest. For a simple interest calculator half yearly payout, each payment = P × R ÷ 200. For a simple interest calculator quarterly payout, each payment = P × R ÷ 400. On ₹1 lakh at 8%, that is ₹4,000 every half-year or ₹2,000 every quarter.

Simple interest calculator for loan and EMI

For a loan quoted at a flat rate, interest = P × R × T ÷ 100 and the EMI = (P + interest) ÷ months. Use the simple interest calculator for flat quotes on a home loan, car loan or education loan, and for education-loan interest during the study period. But EMIs on most bank loans work on a reducing balance, which a simple interest calculator does not show directly – each month's interest is simple interest on the balance left. How to calculate simple interest on a loan repaid in EMIs: use the EMI calculator.

How to calculate simple interest rate

How to calculate simple interest rate: R = 100 × SI ÷ (P × T). What is simple interest formula? SI = P × R × T ÷ 100. What is simple interest in maths? Interest that grows in a straight line – the same amount every period.

What is simple interest and compound interest with example

₹10,000 at 10% for 2 years: simple interest = ₹2,000; compound interest (yearly) = ₹2,100, because in year two you also earn 10% on the first year's ₹1,000. That is what is simple interest and compound interest in simple words. For how to calculate simple interest and compound interest side by side, use this page with the compound interest calculator; the simple interest calculator vs compound interest calculator table above shows the gap over 20 years.

Simple interest calculator for India: rupees per ₹100 and days

In India, informal and gold loans are often quoted "per ₹100 per month" – ₹2 per ₹100 per month means 2% a month, or 24% a year. This simple interest calculator for India lets you choose "per month" so you can enter the rate exactly as the lender states it. Indian banks count interest for days on a 365-day year, so a simple interest calculator for India in days divides the day count by 365.

Simple interest calculator example

A simple interest calculator example: ₹50,000 borrowed at ₹1.50 per ₹100 per month for 8 months. Interest = 50,000 × 1.5% × 8 = ₹6,000, and you repay ₹56,000. The same loan for 120 days at 18% a year costs 50,000 × 18% × 120 ÷ 365 = ₹2,959.

Simple interest calculator monthly payment and EMI

When a loan charges flat (simple) interest, the monthly payment is (principal + total interest) ÷ number of months. On ₹1,00,000 at 10% a year simple interest for 2 years, interest is ₹20,000 and the simple interest calculator's monthly EMI is ₹1,20,000 ÷ 24 = ₹5,000. Interest per year is ₹10,000, so with yearly payments you would pay ₹10,000 of interest each year and return the principal at the end. A flat 10% costs much more than a 10% reducing-balance loan; compare with the EMI calculator.

Simple interest calculator per year and per month

Simple interest per year = P × R ÷ 100; per month it is that figure ÷ 12. ₹2 lakh at 9% earns ₹18,000 per year or ₹1,500 per month.

Simple interest calculator using HTML, CSS and JavaScript

Students often build a simple interest calculator using HTML, CSS and JavaScript as a first project. The JavaScript code needs only one line of maths:

<input id="p"> <input id="r"> <input id="t"> <button onclick="si()">Calculate</button> <p id="out"></p>
<script>
function si() {
  const p = +document.getElementById('p').value, r = +document.getElementById('r').value, t = +document.getElementById('t').value;
  const interest = p * r * t / 100;
  document.getElementById('out').textContent = 'Interest: ' + interest.toFixed(2) + ', Total: ' + (p + interest).toFixed(2);
}
</script>

Style the inputs with CSS as you like; validate that all three values are positive numbers before calculating.

Frequently asked questions

Last updated 2026-09-18