The double type is stored as an eight-byte, double-precision, floating-point number. It represents a double-precision 64-bit IEEE 754 value.
The double type can represent numbers as large as 10308 (positive or negative) with an accuracy of about 15 digits, and as small as 10-323. The double type can also represent NaN (Not a Number), positive and negative infinity, and positive and negative zero.
This type is useful for applications that need large numbers but do not need precise accuracy. If you require very accurate numbers, consider using the Decimal data type.
The corresponding .NET Framework data type is