using System; class BinToDec { static void Main(string[] args) { string binary = "101"; Console.WriteLine(BinaryToDecimal(binary)); // will return 5 } private static long BinaryToDecimal(string binary) { long decimalNum = 0; for (int i = binary.Length - 1, pow = 0; i >= 0; i--, pow++) { decimalNum += int.Parse(binary[i].ToString()) * (long)Math.Pow(2, pow); } return decimalNum; } }