What is the Compound Interest Calculator?
Compound interest means you earn interest not only on the money you put in but also on the interest already added. Over many years this snowball effect makes a big difference, which is why starting early matters more than the exact amount.
The calculator handles a starting deposit, regular monthly contributions (like a SIP in a mutual fund or a monthly savings plan) and different compounding frequencies: yearly, half-yearly, quarterly, monthly or daily. The growth table shows deposits, interest and balance for every year.
How to use the Compound Interest Calculator
- Enter your initial investment.
- Enter how much you will add each month (0 if none).
- Enter the annual interest or profit rate.
- Enter the number of years.
- Choose the compounding frequency and read the future value and growth table.
Formula
A = P × (1 + r/n)^(n·t) plus each monthly deposit compounded for the months it is invested
Example
Investing Rs 100,000 now and Rs 10,000 a month at 12% a year, compounded monthly, grows to about Rs 2.63 million after 10 years. You deposit Rs 1.3 million and earn about Rs 1.33 million in interest.
Simple vs compound interest
With simple interest you earn the same amount every year on your original deposit. With compound interest each year's interest is added to the balance, so the next year's interest is larger. At 10% a year, Rs 100,000 becomes Rs 200,000 after 10 years with simple interest but about Rs 259,374 with yearly compounding.
The rule of 72
Divide 72 by the yearly rate to estimate how many years it takes to double your money. At 12% your money doubles in about 6 years; at 8% it takes about 9 years.
Things to keep in mind
- Returns from savings accounts, certificates and funds are not guaranteed and can change.
- Inflation reduces what your future money can buy.
- Taxes and fees lower the real return.
- Use the Loan Calculator to see the same compounding work against you on debt.
You may also need
People who use the Compound Interest Calculator often need these related tools too:
- Age Calculator: Find your exact age in years, months and days from your date of birth, plus the total days, weeks and hours you have lived and how long until your next birthday. Useful for forms, admissions and job applications that ask for age on a specific date.
- Percentage Calculator: Four percentage calculators on one page: X% of Y, X is what percent of Y, percentage increase or decrease, and adding or removing a percentage. Ideal for marks, discounts, salary raises and price changes.
- Discount Calculator: Work out the final price after a percentage discount and exactly how much you save. Handles extra discounts like "flat 50% + 20% off" and adds sales tax if needed.
Frequently asked questions
What is compound interest?
Interest calculated on both the original amount and the interest already earned, so your balance grows faster over time.
How often should interest be compounded?
More frequent compounding gives a slightly higher result. Monthly compounding earns a little more than yearly at the same rate.
What is the effective annual rate?
The real yearly growth after compounding. 12% compounded monthly is an effective rate of about 12.68%.
Can I use this as a SIP calculator?
Yes. Enter 0 or a lump sum as the initial investment and your monthly SIP amount as the monthly contribution.
How long will it take to double my money?
Use the rule of 72: divide 72 by the yearly rate. At 9% it takes about 8 years.
Is the Compound Interest Calculator free to use?
Yes. The Compound Interest Calculator on Custom Converter is completely free, with no sign-up, no daily limit and no watermark.
Does the Compound Interest Calculator work on mobile phones?
Yes. It is built mobile-first and works on Android phones, iPhones, tablets and computers in any modern browser, with no app to install.