String Format for Double [C#]

The following examples show how to format float numbers to string in C#. You can use static method String.Format or instance methods double.ToString and float.ToString.

Digits after decimal point

This example formats double to string with fixed number of decimal places. For two decimal places use pattern „0.00“. If a float number has less decimal places, the rest digits on the right will be zeroes. If it has more decimal places, the number will be rounded.

[C#]

// just two decimal places

String.Format("{0:0.00}", 123.4567);      // "123.46"

 String.Format("{0:0.00}", 123.4);         // "123.40"

 String.Format("{0:0.00}", 123.0);         // "123.00"  

Next example formats double to string with floating number of decimal places. E.g. for maximal two decimal places use pattern „0.##“.

[C#]

// max. two decimal places

 String.Format("{0:0.##}", 123.4567);      // "123.46"

 String.Format("{0:0.##}", 123.4);         // "123.4"

 String.Format("{0:0.##}", 123.0);         // "123"  

Digits before decimal point

If you want a float number to have any minimal number of digits before decimal point use N-times zero before decimal point. E.g. pattern „00.0“ formats a float number to string with at least two digits before decimal point and one digit after that.

[C#]

// at least two digits before decimal point

 String.Format("{0:00.0}", 123.4567);      // "123.5"

 String.Format("{0:00.0}", 23.4567);       // "23.5"

 String.Format("{0:00.0}", 3.4567);        // "03.5"

 String.Format("{0:00.0}", -3.4567);       // "-03.5"  

Thousands separator

To format double to string with use of thousands separator use zero and comma separator before an usual float formatting pattern, e.g. pattern „0,0.0“ formats the number to use thousands separators and to have one decimal place.

[C#]

String.Format("{0:0,0.0}", 12345.67);     // "12,345.7"

 String.Format("{0:0,0}", 12345.67);       // "12,346"  

Zero

Float numbers between zero and one can be formatted in two ways, with or without leading zero before decimal point. To format number without a leading zero use # before point. For example „#.0“ formats number to have one decimal place and zero to N digits before decimal point (e.g. „.5“ or „123.5“).

Following code shows how can be formatted a zero (of double type).

[C#]

String.Format("{0:0.0}", 0.0);            // "0.0"

 String.Format("{0:0.#}", 0.0);            // "0"

 String.Format("{0:#.0}", 0.0);            // ".0"

 String.Format("{0:#.#}", 0.0);            // ""  

Align numbers with spaces

To align float number to the right use comma „,“ option before the colon. Type comma followed by a number of spaces, e.g. „0,10:0.0“ (this can be used only in String.Format method, not indouble.ToString method). To align numbers to the left use negative number of spaces.

[C#]

String.Format("{0,10:0.0}", 123.4567);    // "     123.5"

 String.Format("{0,-10:0.0}", 123.4567);   // "123.5     "

 String.Format("{0,10:0.0}", -123.4567);   // "    -123.5"

 String.Format("{0,-10:0.0}", -123.4567);  // "-123.5    "  

Custom formatting for negative numbers and zero

If you need to use custom format for negative float numbers or zero, use semicolon separator„;“ to split pattern to three sections. The first section formats positive numbers, the second section formats negative numbers and the third section formats zero. If you omit the last section, zero will be formatted using the first section.

[C#]

String.Format("{0:0.00;minus 0.00;zero}", 123.4567);   // "123.46"

 String.Format("{0:0.00;minus 0.00;zero}", -123.4567);  // "minus 123.46"

 String.Format("{0:0.00;minus 0.00;zero}", 0.0);        // "zero"  

Some funny examples

As you could notice in the previous example, you can put any text into formatting pattern, e.g. before an usual pattern „my text 0.0“. You can even put any text between the zeroes, e.g. „0aaa.bbb0“.

[C#]

String.Format("{0:my number is 0.0}", 12.3);   // "my number is 12.3" String.Format("{0:0aaa.bbb0}", 12.3);          // "12aaa.bbb3"  

See also

• [C#] String Format for Int – format (align) integer numbers
• [C#] String Format for DateTime – format date and time
• [C#] IFormatProvider for Numbers – format and parse float numbers using CultureInfo
• [C#] Custom IFormatProvider – string formatting with custom IFormatProvider
• [C#] Align String with Spaces – how to align text to the right or left
• [C#] Indent String with Spaces – how to indent text with repeated spaces

• MSDN Examples – MSDN examples for custom numeric formatting
• String.Format – MSDN – method to format strings
• Double.ToString – MSDN – formats double to string

Custom Numeric Format Strings in C#

You can create a custom numeric format string, which consists of one or more custom numeric specifiers, to define how to format numeric data. A custom numeric format string is any format string that is not a standard numeric format string.
Custom numeric format specifiers are supported by all of the numeric types in the .NET Framework class library. These include the BigInteger, Byte, Decimal, Double, Int16, Int32, Int64, SByte, Single, UInt16, UInt32, and UInt64 types.

Standard Numeric Format Strings in C#

Standard numeric format strings are used to format common numeric types. A standard numeric format string takes the form Axx, where A is an alphabetic character called the format specifier, and xx is an optional integer called the precision specifier. The precision specifier ranges from 0 to 99 and affects the number of digits in the result. Any numeric format string that contains more than one alphabetic character, including white space, is interpreted as a custom numeric format string. For more information, see Custom Numeric Format Strings.