Compound Interest Calculator
Compound interest reinvests interest as it accrues, so the balance grows faster than under simple interest. The calculator uses A = P·(1 + r/n)^(nt) for discrete compounding or A = P·e^(rt) for continuous, returning both the final amount and the interest earned.
Worked examples
Frequently asked questions
What is the difference between discrete and continuous compounding?
Discrete compounding adds interest n times per year. Continuous compounding takes the limit as n → ∞ and uses the exponential function: A = P·e^(rt).
What value of n should I use?
Use 1 for annual, 2 for semi-annual, 4 for quarterly, 12 for monthly, 365 for daily compounding.
How big is the gap between monthly and continuous compounding?
Surprisingly small. For 5% over 10 years on $1000, monthly gives ≈ $1647 and continuous ≈ $1649 — a difference of about $2.