Compound Interest Calculator
Compound interest is interest that earns interest. Simple interest pays you on your original amount forever; compound interest pays you on your original amount plus every bit of interest already credited. Over a year the difference is trivial. Over thirty years it is the difference between a modest sum and a life-changing one.
This is the most flexible calculator on the site: set any compounding frequency, and add a monthly top-up if you're saving as you go. Switch frequency from Yearly to Daily on the same inputs and you'll see the effect is real but small — frequency is a rounding detail next to rate and time.
How it works
- 01The base formula is A = P × (1 + r/n)^(n×t) — where n is how many times a year interest is credited. More frequent crediting means slightly more interest.
- 02Monthly top-ups are compounded separately as an annuity and added on, so the result reflects both your starting amount and everything you added along the way.
- 03"Interest earned" strips out every rupee you contributed, leaving only what the interest itself generated.
Frequently asked
What is the Rule of 72?+
Divide 72 by your annual return to get roughly the number of years for money to double. At 8% that is 9 years; at 12%, 6 years. It is accurate enough for mental maths and it makes the cost of a low return immediately obvious.
How much does compounding frequency really matter?+
₹1,00,000 at 10% for a year gives ₹10,000 compounded yearly and about ₹10,516 compounded daily. Real, but tiny. Chasing daily compounding while accepting a lower rate is a bad trade — rate and time dominate everything else.
Does compound interest work against me too?+
Yes, and far faster. Credit card debt compounds monthly at 36–48% a year. The same force that builds wealth over decades destroys it over months. If you carry a card balance, clearing it is mathematically the best investment available to you.
What counts as "putting money in"?+
Your starting amount plus every monthly top-up across the whole period. Everything above that line is interest — it is the part you earned without working.