Question 1

What is compound interest and how is it different from simple interest?

Accepted Answer

Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus any accumulated interest, causing the balance to grow exponentially. For example, $10,000 at 5% simple interest earns $500/year forever, but at 5% compound interest, the earned interest also earns interest, resulting in $16,289 after 10 years instead of $15,000.

Question 2

How does compounding frequency affect returns?

Accepted Answer

More frequent compounding means slightly higher returns. Daily compounding yields more than monthly, which yields more than annual, for the same nominal interest rate. The difference is most significant over long time horizons. The formula is A = P(1 + r/n)^(nt), where n is the number of compounding periods per year.

Question 3

Can I include regular monthly contributions in the calculation?

Accepted Answer

Yes. The calculator supports an optional regular contribution field. You can add a fixed monthly or annual contribution amount, and the tool will show how those additional deposits compound alongside your initial principal.

Question 4

What is the Rule of 72 and how does it relate to compound interest?

Accepted Answer

The Rule of 72 is a quick mental math shortcut: divide 72 by the annual interest rate to estimate how many years it takes to double your investment. At 6% annual compound interest, your money doubles in approximately 72 ÷ 6 = 12 years. Use this calculator to get the precise answer.

Question 5

Does the calculator account for taxes or inflation?

Accepted Answer

The base calculation shows nominal (before-tax, before-inflation) growth. You can adjust the interest rate input to approximate after-tax or real (inflation-adjusted) returns. For example, if your investment earns 7% and inflation is 3%, enter 4% to approximate real purchasing-power growth.

Compound Interest Calculator