I need to know how much it is worth

What it is worth in monetary value depends on what condition it is in. Is it a plain 1940 without a mint mark? Or, does it have a "D" or an "S" on it for the mint mark?

Here is a reputable online price guide: PCGS Price Guide
And compare it to actual sales prices of similar item on eBay.

Between the two you'll have an accurate current value.

Tyrin - The 1940 wheat penny as per the 2008 coin book on coin values is 1940 ( no mint mark) Lowest grade G-4, {$.15, Highest not proof , MS-60 is $6.50). 1940 "D" ,same as no mint mark, 1940 "S" G-4 $.15, MS-60 $ 6.75. Proof on all three value is $45.oo. Grades on these coins are as floowes, ::: G-4 , VG-8, F-12, VF-20,EF-40, AU-50, MS-60, Ms-63, PF-63- proof (example 1940- VF-20 _ $.40, "D"- $.60, "S"- $.50, ) The better the condition of the coin , the mint mark, sometimes the age is what makles the value of a coin ,or paper money, sometimes the rarety also affects the value, certain odditys such as double struck, Go to walmart, books a million acoin shop, and get a coin book , or if you want to check on just a few coins go to your local libery and check one out, coin or paper or both . Or come on here and I or someone else will try to help you out, I do have a lot of exper. In coins, and paper money, but I still go to the recent book to make sure I do not quate someone wrong,Values change fast. Another thing the value of a coin or paper money is sometimes higher because the coin to a collector may need that coin to finnish out a certain part of there collection. Example. Say it's a 1931 "S" dimeVF-20, book value $9.00, they need it to finnish out dimes from1916to 1940, so they offer you $15.00 to $25.00 for the coin or even more, In other words the value of a coin or piece of paper money is as high as the person wanting it makes it . The books only give you the value, ::: good luck & GOD BLESS :::: F.B.E.