Facts
Float Type: 32 bit floating point number in the range from approximately
1.5 × 10−45
to 3.4 × 1038 with a precision of 7 digits.
Double Type: 64 bit floating point number in the range from approximately
5.0 × 10−324
to 1.7 × 10308 with a precision of 15-16 digits.
Decimal Type: 128 bit floating point number in the range from approximately
1.0 × 10−28 to 7.9 × 1028 with 28-29 significant digits.
When to use decimal, when to use float/double?
- Use decimal for counted values (like money, scores)
- Use float/double for measured values (like distance)
Microsoft CSharp Language Specification of decimal type
The decimal type
is a 128-bit data type suitable for financial and monetary calculations. The decimal type can represent values ranging from 1.0 × 10−28
to approximately 7.9 × 1028 with 28-29 significant digits.
The finite set of values of type decimal are of the form (–1)s × c × 10-e,
where the sign s is 0 or 1, the coefficient c is given by 0 ≤ c < 296,
and the scale e is such that 0 ≤ e ≤ 28.The decimal type does not support signed zeros, infinities, or NaN's. A decimal is represented as a 96-bit integer scaled by a power of ten. For decimals with an absolute value less than 1.0m, the
value is exact to the 28th decimal place, but no further. For decimals with an absolute value greater than or equal to 1.0m, the value is exact to 28 or 29 digits. Contrary to the float and double data types,
decimal fractional numbers such as 0.1 can be represented exactly in the decimal representation. In the float and double representations, such numbers are often infinite fractions, making
those representations more prone to round-off errors.
If one of the operands of a binary operator
is of type decimal, then the other operand must be
of an integral type or of type decimal. If
an integral type operand is present, it is converted to decimal before the operation is performed.
The result of an operation on values of
type decimal is that which would result from calculating an exact result
(preserving scale, as defined for each operator) and then rounding to fit the
representation. Results are rounded to the nearest representable value, and,
when a result is equally close to two representable values, to the value that
has an even number in the least significant digit position (this is known as
“banker’s rounding”). A zero result always has a sign of 0 and a scale of 0.
If a decimal arithmetic operation produces
a value less than or equal to 5 × 10-29 in absolute value,
the result of the operation becomes zero. If a decimal
arithmetic operation produces a result that is too large for the decimal format, a System.OverflowException is thrown.
The decimal type
has greater precision but smaller range than the floating-point types. Thus,
conversions from the floating-point types to decimal
might produce overflow exceptions, and conversions from decimal to the floating-point types might cause loss of precision. For
these reasons, no implicit conversions exist between the floating-point types
and decimal, and without explicit casts, it is not possible to mix
floating-point and decimal operands in the
same expression.
ref: C# Language Specification 5.0
ref: C# Language Specification 5.0
