You need to provide the denomination in order for us to provide an accurate value.
The average value is around 11.42 and up to 1300 for certain coins that were uncirculated. Most of the value of this coin is due to the silver content.
If the coin shows any wear, value is for the silver at about $6.00
The U.S. stopped making silver dollars in 1935. If you have a coin from a different country please post a new question that includes the name of the country.
If the coin shows any wear at all, the value is for the silver about $2.50 the coin is a very common high mintage year.
Take it to a coin dealer, coin show or a jeweler most buy silver coins for the for the scrap value.
A 1957 cent is all copper. The silver part has been coated with some other metal, so this is a damaged coin with no numismatic value.
The value of a silver coin is always changing because the value of silver is always changing. See the related link below for a silver coin value calculator. This does not give the actual value of the coin but it does give the value of the metal used to make the coin. This is know as the melt value.
The U.S. Mint has never made a Silver Penny . If it is a 1957 Lincoln cent, it has likely been chrome plated which can look like silver. This is very common but the coin does not have any numismatic value.
The US Mint did not produce any silver wheat cents in 1957. If you have one it has been coated with something after it left to mint. Coins such as this have very little numismatic {fancy word for coin collecting} value.
Metal value depends on the purity of the silver and the weight of the coin. Numismatic value depends on the condition of the coin.
A Silver Eagle Bullion coin is 99.9% pure silver and weighs 1 oz per coin. The stamped value of the coin is U.S$1 however the intrinsic value of the coin is the value of the silver within that coin. If the the spot price of silver was $30oz at the time of checking, then the value of that coin would be worth at least $30 or more.
There's no such thing as a U.S. silver dollar coin from 1957.