Compound Interest Calculator

This is the standard spreadsheet model (nominal annual rate divided by the number of periods). It is not a particular bank’s APY disclosure. Numbers stay in your browser. The default is 10,000 at 5% compounded monthly for three years, which grows to 11,614.72.

Quick answer: with a starting amount in B2, an annual rate in C2 (as 5% or 0.05), years in D2 and compounds per year in E2, Excel and Google Sheets can use either of these:

=B2*(1+C2/E2)^(E2*D2)
=FV(C2/E2, E2*D2, 0, -B2)

The two should match. Typing 5 in C2, rather than 5% or 0.05, treats the rate as 500% a year.

$10,000 at 5%, compounded monthly for three years

There are 36 monthly periods, and the rate per period is 0.05 ÷ 12. In Google Sheets on 12 November 2026, both of the following returned 11614.722313334678 (about $11,614.72):

=FV(0.05/12, 36, 0, -10000)
=10000*(1+0.05/12)^(12*3)

Interest earned is that future value minus the 10,000 you started with, about $1,614.72. The same starting amount compounded annually at 6% for two years is =5000*(1.06^2), which returned 5618.000000000001, a floating-point stand-in for the exact 5,618.

Continuous compounding uses a different formula, =10000*EXP(0.05*3), which returned 11618.34242728283 in the same sheet — a few dollars more than monthly compounding over these three years. This calculator’s continuous option is for a single starting amount only; it does not add a regular contribution.

Adding a regular contribution

The FV payment argument is the amount added each compounding period. A $200 deposit at the end of every month, on top of the $10,000, for the same three years and 5% monthly rate:

=FV(0.05/12, 36, -200, -10000)

returned 19365.38941734113. Of that, 36 × 200 = 7,200 is money you added, 10,000 is the original principal, and the rest is interest. The contribution has to use the same period as compounding: monthly compounding with a monthly deposit, quarterly with a quarterly deposit. If your deposits and your compounding do not line up, this one FV call is the wrong model.

Deposits at the beginning of each period earn one extra period of interest. In Sheets, that is the type argument at the end of FV. Twelve beginning-of-month deposits of $100 at 5% monthly, with no starting balance, were =FV(0.05/12,12,-100,0,1), which returned 1233.0017389497646. A zero rate is simpler: =FV(0,24,-100,-10000) was exactly 12400, which is 10,000 plus 24 × 100, with no interest.

What this is not

If you already know the starting and ending balances and want the implied annual rate, that is CAGR (or RRI), not this page. Compound interest also assumes the stated nominal rate is divided evenly across periods. A bank APY already includes compounding; feeding an APY into this calculator as if it were a nominal rate will overstate the result. Taxes, fees, and rate changes are not in the formula.

Questions that come up

What is the compound interest formula in Excel or Google Sheets?

For a starting amount in B2, an annual rate in C2, years in D2 and compounds per year in E2, use =B2*(1+C2/E2)^(E2*D2), or =FV(C2/E2,E2*D2,0,-B2). Enter the rate as 5% or 0.05, not 5.

How do I include a regular contribution?

Use FV and put the contribution in the payment argument, with a negative sign if the starting amount is also entered as a negative (money you invest). Monthly deposits of 200 for three years on top of 10,000, at 5% compounded monthly, are =FV(0.05/12,36,-200,-10000).

Is this the same as CAGR?

No. Compound interest projects a future value from a rate you already have. CAGR works backwards from a start value and an end value to find the rate. Use the CAGR calculator when you know both balances and want the implied annual rate.