Compound Interest Calculator
Model A = P(1 + r/n)nt, continuous compounding, or add monthly contributions. Compare the effective annual rate (EAR) when compounding frequency changes.
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Results
Final amount
Year-by-year balance
| Year | Balance | Interest so far |
|---|
Ideas behind compounding
Albert Einstein is often quoted as calling compound interest “the eighth wonder of the world” — the quote is widely attributed but not well verified. The underlying idea is sound: when interest earns interest, growth accelerates over long horizons.
Rule of 72: roughly 72 ÷ annual percent rate estimates years to double money at constant compounded growth (handy, not exact).
EAR: The effective annual rate lets you compare nominal rates that compound at different frequencies — more frequent compounding within the year lifts the effective yield slightly.
This page is currency-agnostic — pick a display currency; math is the same. Fees, tax, and inflation are not modeled.
Frequently asked questions
What is compound interest?
Interest on your principal and on interest already added — growth speeds up versus simple interest.
What is EAR?
Effective annual rate: the yearly equivalent after compounding. More compounding within the year → higher EAR for the same nominal rate.
Does currency change the math?
No — only display formatting.
Can I model monthly deposits?
Yes — use the optional monthly contribution field.
Is my data uploaded?
No — calculations run locally in your browser.
Related tools
SIP and lumpsum calculators explore monthly vs one-time investing.