Floating-point numeric types (C# reference)

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29. 09. 2022.

The floating-point numeric types represent real numbers. All floating-point numeric types are value types. They are also simple types and can be initialized with literals. All floating-point numeric types support arithmetic, comparison, and equality operators.

Characteristics of the floating-point types

C# supports the following predefined floating-point types:

C# type/keyword	Approximate range	Precision	Size	.NET type
`float`	±1.5 x 10⁻⁴⁵ to ±3.4 x 10³⁸	~6-9 digits	4 bytes	System.Single
`double`	±5.0 × 10⁻³²⁴ to ±1.7 × 10³⁰⁸	~15-17 digits	8 bytes	System.Double
`decimal`	±1.0 x 10^-28 to ±7.9228 x 10²⁸	28-29 digits	16 bytes	System.Decimal

In the preceding table, each C# type keyword from the leftmost column is an alias for the corresponding .NET type. They are interchangeable. For example, the following declarations declare variables of the same type:

double a = 12.3;
System.Double b = 12.3;

The default value of each floating-point type is zero, 0. Each of the floating-point types has the MinValue and MaxValue constants that provide the minimum and maximum finite value of that type. The float and double types also provide constants that represent not-a-number and infinity values. For example, the double type provides the following constants: Double.NaN, Double.NegativeInfinity, and Double.PositiveInfinity.

The decimal type is appropriate when the required degree of precision is determined by the number of digits to the right of the decimal point. Such numbers are commonly used in financial applications, for currency amounts (for example, $1.00), interest rates (for example, 2.625%), and so forth. Even numbers that are precise to only one decimal digit are handled more accurately by the decimal type: 0.1, for example, can be exactly represented by a decimal instance, while there's no double or float instance that exactly represents 0.1. Because of this difference in numeric types, unexpected rounding errors can occur in arithmetic calculations when you use double or float for decimal data. You can use double instead of decimal when optimizing performance is more important than ensuring accuracy. However, any difference in performance would go unnoticed by all but the most calculation-intensive applications. Another possible reason to avoid decimal is to minimize storage requirements. For example, ML.NET uses float because the difference between 4 bytes and 16 bytes adds up for very large data sets. For more information, see System.Decimal.

You can mix integral types and the float and double types in an expression. In this case, integral types are implicitly converted to one of the floating-point types and, if necessary, the float type is implicitly converted to double. The expression is evaluated as follows:

If there is double type in the expression, the expression evaluates to double, or to bool in relational and equality comparisons.
If there is no double type in the expression, the expression evaluates to float, or to bool in relational and equality comparisons.

You can also mix integral types and the decimal type in an expression. In this case, integral types are implicitly converted to the decimal type and the expression evaluates to decimal, or to bool in relational and equality comparisons.

You cannot mix the decimal type with the float and double types in an expression. In this case, if you want to perform arithmetic, comparison, or equality operations, you must explicitly convert the operands either from or to the decimal type, as the following example shows:

double a = 1.0;
decimal b = 2.1m;
Console.WriteLine(a + (double)b);
Console.WriteLine((decimal)a + b);

You can use either standard numeric format strings or custom numeric format strings to format a floating-point value.

Real literals

The type of a real literal is determined by its suffix as follows:

The literal without suffix or with the d or D suffix is of type double
The literal with the f or F suffix is of type float
The literal with the m or M suffix is of type decimal

The following code demonstrates an example of each:

double d = 3D;
d = 4d;
d = 3.934_001;

float f = 3_000.5F;
f = 5.4f;

decimal myMoney = 3_000.5m;
myMoney = 400.75M;

The preceding example also shows the use of _ as a digit separator. You can use the digit separator with all kinds of numeric literals.

You can also use scientific notation, that is, specify an exponent part of a real literal, as the following example shows:

double d = 0.42e2;
Console.WriteLine(d);  // output 42

float f = 134.45E-2f;
Console.WriteLine(f);  // output: 1.3445

decimal m = 1.5E6m;
Console.WriteLine(m);  // output: 1500000

Conversions

There is only one implicit conversion between floating-point numeric types: from float to double. However, you can convert any floating-point type to any other floating-point type with the explicit cast. For more information, see Built-in numeric conversions.

C# language specification

For more information, see the following sections of the C# language specification:

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