Formatting Decimals in C#

In this post I am going to show you a few different ways how you can format a decimal number (float, double, or decimal).

Setting the Maximum Allowed Decimal Places

To format your numbers to a maximum of two decimal places use the format string {0:0.##} as shown in the below example:

string.Format("{0:0.##}", 256.583); // "256.58"
string.Format("{0:0.##}", 256.586); // "256.59"
string.Format("{0:0.##}", 256.58);  // "256.58"
string.Format("{0:0.##}", 256.5);   // "256.5"
string.Format("{0:0.##}", 256.0);   // "256"

Setting a Fixed Amount of Decimal Places

This is similar to the above example but instead of hashes (‘#’) in our format string we are going to use zeroes (‘0’) as shown below:

string.Format("{0:0.00}", 256.583); // "256.58"
string.Format("{0:0.00}", 256.586); // "256.59"
string.Format("{0:0.00}", 256.58);  // "256.58"
string.Format("{0:0.00}", 256.5);   // "256.50"
string.Format("{0:0.00}", 256.0);   // "256.00"

The Thousand Separator

To format your decimal number using the thousand separator, use the format string {0:0,0} as shown in the below example:

string.Format("{0:0,0.00}", 1234256.583); // "1,234,256.58"
string.Format("{0:0,0}", 1234256.583);    // "1,234,257"

Setting a Fixed Amount of Digits Before the Decimal Point

To set a minimum amount of three digits before the decimal point use the format string {0:000.##}.

string.Format("{0:00.000}", 1.2345);    // "01.235"
string.Format("{0:000.000}", 12.345);   // "012.345"
string.Format("{0:0000.000}", 123.456); // "0123.456"

Alignment

To specify alignment to the Format method you must write your format string as shown below. Note we are using a comma (‘,’) to specify the number of characters used for alignment.

{0,[no. of chars]} and if you want to pad with zeroes {0,[no. of chars]:00.00}

string.Format("{0,7:##.00}", 2.356);  // "   2.36"
string.Format("{0,-7:##.00}", 2.356); // "2.36   "
string.Format("{0,7:00.00}", 2.356);  // "  02.36"
string.Format("{0,-7:00.00}", 2.356); // "02.36  "

Positive Numbers, Negative Numbers, and Zero

You can include different formats for positive numbers, negative numbers, and zero by using the semicolon character (‘;’).

Format string:
{0:[positive];[negative];[zero]}

string.Format("{0:000.000;(000.000);zero}", 23.43);  // "023.430"
string.Format("{0:000.000;(000.000);zero}", -23.43); // "(023.430)"
string.Format("{0:000.000;(000.000);zero}", 0.0);    // "zero"

Some Pre-Defined Formats

string.Format("{0:C}", 1532.236);  // "£1,532.24"
string.Format("{0:C}", -1532.236); // "-£1,532.24"
string.Format("{0:E}", 1532.236);  // "1.532236E+003"
string.Format("{0:E}", -1532.236); // "-1.532236E+003"
string.Format("{0:F}", 1532.24);   // "1532.24"
string.Format("{0:F}", -1532.24);  // "-1532.24"
string.Format("{0:G}", 1532.236);  // "1532.236"
string.Format("{0:G}", -1532.236); // "-1532.236"
string.Format("{0:N}", 1532.236);  // "1,532.24"
string.Format("{0:N}", -1532.236); // "-1,532.24"
string.Format("{0:P}", 0.1532);    // "15.32 %"
string.Format("{0:P}", -0.1532);   // "-15.32 %"
string.Format("{0:R}", 1532.236);  // "1532.236"
string.Format("{0:R}", -1532.236); // "-1532.236"

Happy formatting. 🙂
Dave