Compound Interest Calculator at a glance
- What it does
- Calculate compound interest with any compounding frequency, see the effect of regular contributions, and understand why frequency matters less than rate.
- Where it runs
- Entirely in your browser — no data is uploaded
- Works offline
- Yes, once the page has loaded
- Cost
- Free, with no account and no usage limit
- Category
- Financial Calculators
How to use the calculator
- Enter the principal you are starting with.
- Enter the annual interest rate.
- Choose the compounding frequency - how often interest is added to the balance.
- Set the period and read the final amount and the interest earned.
The formula
A = P × (1 + r/n)^(n×t)
P = principal
r = annual rate as a decimal
n = compounding periods per year
t = yearsWorked example. ₹1,00,000 at 8% compounded quarterly for 10 years: 1,00,000 × (1 + 0.08/4)40 = about ₹2,20,800. Simple interest over the same period would have produced ₹1,80,000, so compounding added roughly ₹40,800.
Simple versus compound
Simple interest is calculated only on the original principal. Compound interest is calculated on principal plus accumulated interest, so the base grows each period.
| Years | Simple at 8% | Compound at 8% annually |
|---|---|---|
| 5 | ₹1,40,000 | ₹1,46,933 |
| 10 | ₹1,80,000 | ₹2,15,892 |
| 20 | ₹2,60,000 | ₹4,66,096 |
| 30 | ₹3,40,000 | ₹10,06,266 |
At five years the difference is modest. At thirty it is nearly three times. This is why time is the variable that matters most in long-term saving, and why credit card debt left to accumulate becomes unmanageable so quickly.
Does compounding frequency matter?
Less than people expect. ₹1,00,000 at 8% for 10 years:
| Frequency | Final amount |
|---|---|
| Annually | ₹2,15,892 |
| Quarterly | ₹2,20,804 |
| Monthly | ₹2,21,964 |
| Daily | ₹2,22,530 |
| Continuously | ₹2,22,554 |
Moving from annual to quarterly gains about 2%. Everything beyond monthly is negligible. So when a product advertises daily compounding as a feature, it is worth checking whether the rate itself is competitive - that is where the real difference lies.
The comparable figure is the effective annual rate, which converts any compounding frequency to an annual equivalent. Regulations in most countries require it to be shown, precisely so that products can be compared honestly.
Adding to the balance regularly
Compounding a lump sum is powerful; compounding a lump sum plus regular contributions is much more so. ₹1,00,000 at 8% for 20 years grows to about ₹4.66 lakh. Adding ₹5,000 a month over the same period brings the total to roughly ₹34 lakh, because each contribution starts compounding from the day it is made.
The SIP calculator handles the regular-contribution case directly, and is the right tool if that is your situation.
Compounding works in both directions
The same mathematics governs debt. A credit card at 36% a year, compounded monthly, has an effective rate of about 42.6%. A ₹1,00,000 balance left untouched becomes roughly ₹2,03,000 in two years.
Minimum payments are structured so that most of the payment covers interest, which is why a balance serviced at the minimum can take decades to clear. The practical rule: clear high-interest debt before pursuing any investment return, because a guaranteed 36% saved beats an uncertain 12% earned every time.
This is a calculator, not advice. It applies a standard formula to the figures you enter and assumes a constant rate of return, no taxes and no fees unless stated. Real markets do not behave that way. Nothing here is a recommendation to buy, sell or hold any investment — see our full disclaimer, and speak to a qualified adviser regulated in your jurisdiction before making a financial decision.
Frequently asked questions
Simple interest is calculated only on the original amount. Compound interest is calculated on the amount plus previously earned interest, so growth accelerates. Over long periods the difference is very large.
Annual to quarterly gains a couple of percent over a decade. Beyond monthly the gains are negligible. The rate matters far more than the frequency.
The rate that would produce the same result with annual compounding. It is the only fair way to compare two products with different compounding frequencies, and most jurisdictions require it to be disclosed.
Divide 72 by the annual percentage rate for a close approximation. At 8%, about nine years.
No. Interest is usually taxable, and inflation erodes purchasing power. Both reduce the real value of the result - use the inflation calculator to see the difference.
Nothing you enter here leaves your browser
Compound Interest Calculator does its work in JavaScript running on your own device. The page loads once, and after that there is no upload step and no server involved — which matters here because your income, loan and savings figures are nobody else’s business.
You can verify this rather than taking our word for it: load the page, disconnect from the internet, and the tool keeps working. Our privacy policy sets out what is and is not collected, and this guide explains why the distinction matters.