Interest Calculator – Simple & Compound Interest Calculator

Use this free interest calculator to calculate interest in rupees on any amount, for any period. Choose simple interest or compound interest, enter the amount, interest rate and time in days, months or years, and the calculator shows the interest earned, the maturity amount and the maturity date instantly.

You can also tap a bank name below to load the current FD interest rate of SBI, HDFC, ICICI, Axis Bank or Post Office and calculate FD interest without typing the rate yourself.

What Is an Interest Calculator?

An interest calculator is a free online tool that works out how much interest an amount of money will earn, or how much interest you will pay on a loan, without doing the maths by hand. You enter three things: the amount (principal), the interest rate per year, and the time period. The tool then gives you the interest and the total amount at the end of the period.

Almost every money decision in India runs on interest. A fixed deposit, a savings account, a Post Office scheme, a personal loan and a credit card all use either simple interest or compound interest. If you know which type applies and what the numbers come to, you can compare two banks, two schemes or two loan offers in minutes instead of guessing. That is exactly what this page helps you do: one calculator for both types of interest, with the current FD rates of major banks built in.

How to Use This Interest Calculator

1. Choose the interest type. Select Compound Interest for FDs, savings schemes and investments, where interest is added to your balance and itself earns interest. Select Simple Interest for most short-term loans and informal lending, where interest is charged only on the original amount.
2. Enter the amount and rate. Type the principal in rupees and the yearly interest rate. If you want a bank FD rate, tap SBI, HDFC, ICICI, Axis Bank or Post Office above the form and the current rate for your period loads on its own.
3. Set the time period. You can enter the period in years, months or days. This matters because real FD tenures are often odd periods like 15 months or 400 days, and this calculator accepts all three.
4. For compound interest, set the compounding frequency. Bank FDs compound quarterly, savings accounts compound quarterly too, and some schemes compound yearly. The more frequently interest is compounded, the more you earn.
5. Read the result. You get the maturity amount, total interest, average interest per month and per year, the maturity date, a step-by-step calculation and a year-wise growth table.

Interest Calculator Formula

There are two formulas behind every interest calculation. Which one applies depends on whether the interest itself earns further interest or not.

Simple Interest Formula

The total amount at the end is simply Principal + Simple Interest. If the period is given in months, divide the months by 12 to get T. If it is given in days, divide the days by 365.

Compound Interest Formula

Compound Interest = Amount – Principal. The calculator above applies these two formulas exactly, so the result you see is the same result you would get by working through the steps yourself.

Simple Interest Calculator: How Simple Interest Works

Simple interest is always calculated on the original principal, and only on the principal. The interest amount stays the same every year, because the base never grows. If you deposit Rs 50,000 at 8% simple interest, you earn Rs 4,000 in the first year, Rs 4,000 in the second year and Rs 4,000 in the third year. Nothing changes, because the interest you earned is never added to the base.

Worked example. Rs 50,000 at 8% per year for 3 years:

• Simple Interest = 50,000 x 8 x 3 / 100 = Rs 12,000
• Total amount after 3 years = 50,000 + 12,000 = Rs 62,000

Simple interest is used where money is borrowed or lent for a short, fixed period: many personal loans from informal sources, some short-term credit arrangements, and the interest charged on late payments. It is also the base formula taught in schools, because every other interest calculation builds on it. Use the Simple Interest mode of the calculator above whenever the interest does not get added to the principal during the period.

One point that confuses many people: banks almost never pay simple interest on deposits. If a bank quotes you an FD rate, that interest is compounded, usually every quarter. So for any deposit calculation, use the compound mode.

Compound Interest Calculator: Interest on Interest Explained

Compound interest is interest calculated not only on your principal, but also on the interest that has already been added to it. That is why it is often called an interest on interest calculator: after the first compounding period, your interest starts earning interest of its own. In banking and finance this same idea is also called complex interest.

Worked example. The same Rs 50,000 at 8% for 3 years, compounded yearly:

• After year 1: 50,000 + 4,000 = Rs 54,000
• After year 2: 54,000 + 4,320 = Rs 58,320 (the extra Rs 320 is interest on the first year’s interest)
• After year 3: 58,320 + 4,665.60 = Rs 62,986
• Compound interest earned = Rs 12,986, which is Rs 986 more than the Rs 12,000 from simple interest

Over 3 years the difference looks small. Over 10 or 20 years it becomes very large, because the interest part itself keeps growing. This is the reason long-term deposits and investments are always quoted with compounding.

Compounding Frequency: More Frequent Means More Interest

For the same rate and the same period, interest compounded more often gives a slightly higher return. Here is Rs 1,00,000 at 10% for 1 year, compounded at different frequencies:

The order never changes: daily compounding earns the most, then monthly, then quarterly, then half-yearly, then yearly. Indian bank FDs use quarterly compounding, which is why the calculator above has Quarterly selected by default. When you compare two deposit offers, compare them at the same compounding frequency, otherwise the comparison is not fair.

Simple Interest vs Compound Interest

Same numbers, both methods. Rs 1,00,000 at 7% for 5 years:

• Simple interest: 1,00,000 x 7 x 5 / 100 = Rs 35,000. Total = Rs 1,35,000
• Compound interest (yearly): Rs 1,00,000 grows to Rs 1,40,255. Interest = Rs 40,255
• Compounding pays Rs 5,255 extra on the same amount, same rate and same period

If the same deposit compounds quarterly, like a bank FD, the total becomes Rs 1,41,478 and the extra rises to Rs 6,478. Try both modes in the calculator with your own numbers and watch the difference grow with the period.

FD Interest Calculator: SBI, HDFC, ICICI, Axis Bank and Post Office Rates

A fixed deposit is the most common use of an interest calculator in India, so this page carries the current FD rates built into the tool itself. Tap a bank name in the calculator and the rate for your chosen period fills in automatically. Banks compound FD interest every quarter, so keep the compounding frequency on Quarterly for any FD calculation.

FD interest rates as of October 2026, for deposits below Rs 3 crore, general public:

Senior citizens get 0.50% extra on bank FDs, which is why the calculator has a senior citizen option. Post Office rates do not change with age. Rates change whenever banks revise them, so confirm the final rate with your bank branch or its official website before depositing.

Worked FD example. Rs 1,00,000 in an SBI FD at 6.25% for 1 year, compounded quarterly: the deposit grows to Rs 1,06,398, so the FD interest is Rs 6,398. Note that the interest is more than a plain 6.25% of 1 lakh (Rs 6,250), because each quarter’s interest earns interest in the next quarter.

For a dedicated tool with monthly payout options, special tenure like 444 days and per-bank examples, use our FD Calculator. If you deposit a fixed amount every month instead of one lump sum, use the RD Calculator.

Monthly Interest on Rs 1 Lakh: Rate-wise Table

Many people search for the monthly interest they can get on 1 lakh. For a monthly payout deposit, the monthly interest is approximately the yearly interest divided by 12:

These are approximate payout figures. In a cumulative FD the same money compounds quarterly and gives a little more at maturity, as the SBI example above shows.

Interest Calculator in Months and Days

Not every period is a neat number of years. FDs run from 7 days to 10 years, loans are taken for 18 or 30 months, and money is often parked for a few months between two expenses. This calculator accepts the period in days and months directly, so you do not have to convert anything yourself.

The conversion happening behind the scenes is simple: months are divided by 12 and days are divided by 365 to get the time in years, and then the same formula is applied. For example, Rs 1,00,000 at 6% simple interest for 180 days earns 1,00,000 x 6 x (180/365) / 100 = Rs 2,959. Select Days or Months in the time period field and enter your exact period to get the same result for compound interest as well, along with the exact maturity date.

Loan Interest Calculator: The Interest You Pay

The same calculator also works in reverse thinking: it shows the interest cost of borrowing. But be careful about one difference. When a loan is quoted at a flat rate, interest is charged on the full original amount for the whole period, and the simple interest formula applies directly. A Rs 2,00,000 loan at 12% flat for 2 years costs 2,00,000 x 12 x 2 / 100 = Rs 48,000 in interest.

Bank and NBFC loans, however, are almost always on a reducing balance basis. There, interest is charged only on the amount still outstanding, which falls with every EMI. The same Rs 2,00,000 loan at 12% for 2 years on reducing balance costs roughly Rs 26,000 in total interest, about half of the flat-rate cost. So whenever you compare a loan offer, first check whether the quoted rate is flat or reducing. A 10% flat rate is roughly equal to an 18% to 19% reducing balance rate. Use the simple interest mode above to estimate flat-rate loans, and treat the result as the maximum cost for reducing-balance loans.

Rule of 72: How Fast Your Money Doubles

The Rule of 72 is a shortcut that works only with compound interest. Divide 72 by the yearly interest rate and you get the approximate number of years in which your money doubles. At 6% your money doubles in about 12 years, at 8% in about 9 years, and at 12% in about 6 years. It is a quick way to judge whether a rate is worth a long lock-in, before you run the full calculation above.

Disclaimer: This calculator is for education and estimation only. Bank interest rates change from time to time, and the final interest is calculated by your bank as per its own rules. Please confirm the applicable rate and maturity value with your bank before depositing. Page last updated: November 2026. FD rates shown are as of October 2026.

Frequently Asked Questions