Parse and render Excel number format strings
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Latest commit c997e89 Feb 7, 2018


.NET library to parse ECMA-376 number format strings and format values like Excel and other spreadsheet softwares.

Build status

Install via NuGet

If you want to include ExcelNumberFormat in your project, you can install it directly from NuGet

To install ExcelNumberFormat, run the following command in the Package Manager Console

PM> Install-Package ExcelNumberFormat


var format = new NumberFormat("#.##");
Console.WriteLine(format.Format(1234.56, CultureInfo.InvariantCulture));


  • Parses and formats most custom number formats as expected: decimal, percent, thousands, exponential, fraction, currency, date/time, duration, text.
  • Supports multiple sections with conditions.
  • Formats values with relevant constants from CultureInfo.
  • Formats dates and durations using DateTime and TimeSpan values instead of numeric values like Excel.
  • Targets net20 and netstandard1.0 for max compatibility.

Formatting .NET types

The Format() method takes a value of type object as parameter. Internally, the value is cast or converted to a specific .NET type depending on the kind of number format:

Format Kind Example .NET type Conversion strategy
Number 0.00 double Convert.ToDouble()
Fraction 0/0 double Convert.ToDouble()
Exponent #0.0E+0 double Convert.ToDouble()
Date/Time hh:mm DateTime Convert.ToDateTime()
Duration [hh]:mm TimeSpan Cast to TimeSpan
General General (any) Convert.ToString()
Text ;;;"Text: "@ string Convert.ToString()

In case of errors, Format() returns the value from Convert.ToString().


  • 'General' is formatted with .ToString() instead of Excel conventions.
  • No errors: Invalid format strings and incompatible input values are formatted with .ToString().
  • No color information.
  • Variable width space is returned as regular space.
  • Repeat-to-fill characters are printed once, not repeated.
  • No alignment hinting.
  • No date conditions.