Question 1

What is compound interest?

Accepted Answer

Interest calculated on the initial principal and on accumulated interest from previous periods.

Question 2

What formula does the calculator use?

Accepted Answer

A = P*(1 + r/n)^(n*t). With contributions: FV = P*(1 + r/n)^(n*t) + PMT*(((1 + r/n)^(n*t) - 1)/(r/n)) for end-of-period payments.

Question 3

What is APY/EAR?

Accepted Answer

Effective Annual Rate accounts for compounding: (1 + r/n)^n - 1.

Question 4

How do contributions timing affect results?

Accepted Answer

Start-of-period contributions earn one extra period: multiply the PMT term by (1 + r/n).

Question 5

Can the calculator handle negative returns or fees?

Accepted Answer

Yes—enter a net rate (after fees) or add annual fee as a negative cash flow.

Compound Interest Calculator