C# Fixed-Point ("F") Format Specifier

The Fixed-Point ("F") format specifier in C# converts a number to a string with a fixed number of decimal places. It produces output in the form "-ddd.ddd..." where "d" represents a digit (0-9). The negative sign appears only for negative numbers.

Syntax

Following is the syntax for using the Fixed-Point format specifier −

number.ToString("F")          // Default 2 decimal places
number.ToString("Fn")         // n decimal places (0-99)
number.ToString("F", culture) // With specific culture

Default Precision

When no precision is specified, the "F" format specifier defaults to 2 decimal places −

using System;

class Program {
    static void Main() {
        int value1 = 212;
        double value2 = 45.7;
        Console.WriteLine(value1.ToString("F"));
        Console.WriteLine(value2.ToString("F"));
    }
}

The output of the above code is −

212.00
45.70

Custom Precision

You can specify the exact number of decimal places using "Fn" where n is a number from 0 to 99 −

using System;
using System.Globalization;

class Program {
    static void Main() {
        int val1 = 38788;
        int val2 = -344;
        double val3 = 5656.789;
        
        Console.WriteLine(val1.ToString("F", CultureInfo.InvariantCulture));
        Console.WriteLine(val2.ToString("F3", CultureInfo.InvariantCulture));
        Console.WriteLine(val3.ToString("F5", CultureInfo.InvariantCulture));
        Console.WriteLine(val3.ToString("F0", CultureInfo.InvariantCulture));
    }
}

The output of the above code is −

38788.00
-344.000
5656.78900
5657

Rounding Behavior

The Fixed-Point format specifier uses banker's rounding (round to nearest even) when the value needs to be rounded −

using System;

class Program {
    static void Main() {
        double value1 = 2.125;
        double value2 = 2.135;
        double value3 = 2.145;
        
        Console.WriteLine($"{value1} -> {value1.ToString("F2")}");
        Console.WriteLine($"{value2} -> {value2.ToString("F2")}");
        Console.WriteLine($"{value3} -> {value3.ToString("F2")}");
    }
}

The output of the above code is −

2.125 -> 2.12
2.135 -> 2.14
2.145 -> 2.14

Comparison with Other Format Specifiers

Conclusion

The Fixed-Point ("F") format specifier in C# provides precise control over decimal places in numeric output. It defaults to 2 decimal places but accepts custom precision from 0 to 99, making it ideal for financial calculations and formatted numeric displays where consistent decimal alignment is required.