How much is an 1827 silver dollar worth?

It would be an incredible find because there are no 1827 dollar coins. The U.S. didn't make any dollars for circulation between 1804 and 1835 inclusive.

Please check your coin again. If it's a different denomination, please post a new question. If it says "1 dollar" you have a counterfeit - the market has been flooded with fakes, mostly from the Far East. Some are very good, and others are laughably bad with impossible dates and designs. I've seen an "1865 Washington quarter" and an "Indian head cent" where the date was upside down!