Ounces per milliliter to milligrams per liter conversion calculator above calculates how many milligrams per liter are in 'X' ounces per milliliter (where 'X' is the number of ounces per milliliter to convert to milligrams per liter). In order to convert a value from ounces per milliliter to milligrams per liter (from oz/mL to mg/L) type the number of oz/mL to be converted to mg/L and then click on the 'convert' button.