Compound interest is interest calculated on both your original amount AND the interest already earned. Formula: A = P(1 + r/n)^(nt). Example: $10,000 at 8% annual interest compounded monthly for 10 years grows to $22,196 — more than double! Einstein reportedly called this 'the eighth wonder of the world.'
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💹 Compound Interest Calculator
See exactly how compound interest grows your money over time. Compare daily, monthly, and annual compounding. Discover why starting to save early makes an enormous difference!
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🤔 How Does This Work?
Compound interest uses this formula:
A = P x (1 + r/n)^(n x t)
A = Final amount (what you end up with)
P = Principal (starting amount)
r = Annual interest rate (as a decimal, e.g. 0.08 for 8%)
n = Number of times interest compounds per year
t = Number of years
Our calculator shows your final amount, total interest earned, and the percentage growth — so you can see the incredible power of compounding over time.
✅ Trusted Tool
The 365tool.net Compound Interest Calculator uses the internationally standard compound interest formula used by banks, financial advisors, and investment firms worldwide. 100% free, no sign-up, works for any currency.
❓ FAQ
What is compound interest in simple words?▼
Compound interest means your interest earns more interest. If you have 10,000 rupees and earn 10% interest, you get 1,000. Next year, you earn 10% on 11,000 — that is 1,100. Each year the interest grows because it builds on itself!
How is compound interest different from simple interest?▼
Simple interest: you earn the same amount each year (only on original amount). Compound interest: you earn more each year (on original amount PLUS all previous interest). Over time, compound interest grows dramatically more.
How often should interest compound?▼
More frequent compounding = more money. Daily compounding earns slightly more than monthly, which earns more than annually. However, the difference between daily and monthly is usually small. What matters most is starting early and keeping your money invested.
What is the Rule of 72?▼
The Rule of 72 is a quick way to find how long it takes to double your money. Divide 72 by your annual interest rate. Example: at 8% interest, 72 / 8 = 9 years to double your money. At 6% it takes 12 years. At 12% it takes just 6 years!
Why does starting early matter so much for compound interest?▼
Time is the most powerful ingredient in compound interest. 10,000 invested at 8% for 40 years grows to 217,245. The same amount for only 20 years grows to just 46,610. Starting 20 years earlier gives you 4.7 times more money! This is why starting to save young is so important.