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Posted 22 Dec 2006


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Number base conversion class in C#

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22 Dec 20063 min read
Library class to convert numbers between any number bases (from 2 to 36)

Sample Image - Convert.gif


This library class converts numbers between a variety of number bases - in fact, any number base between 2 (binary) and 36. This goes beyond the .NET framework conversion libraries which offer a limited set of conversions

The library exposes a number of common conversions (such as Binary to Decimal/base10) for simple use as well as allowing user defined conversions under advanced use (such as base 26 to base 5)


Recently I needed to calculate the numeric column ordinals for an Excel spreadsheet. Columns begin at 'A' and continue to 'B, ..., Z, AA, AB, ...' etc. I could not find any code to do this anywhere and also came across a number of posts on various coding sites asking how to perform conversions between arbitrary number bases

I solved my Excel requirement using a short function but decided it would be a useful exercise to develop a general number conversion class - this is the result. This class is generic enough to include handling the Excel scenario as well as all conventional number bases from 2 to 36 (inclusive)

The actual process of converting between bases is fairly trivial and I chose to convert to base 10 as an interim step. Therefore, when converting from base 3 to 7, for example, the code converts from base 3 to 10 then 10 to 7. I'm sure it is possible to develop a single algorithm to perform the conversion in one step so this may appear in a later version although I feel the current solution is easier to maintain and debug so maybe not

Code structure

There are 3 projects in the attached solution:

  • - Conversion class library
  • - Unit tests (requires NUnit)
  • - UI demo (see screenshot above)

Using the code

A simple demo is included. Download the code, open the solution, set the Demo project as startup and run. This will start the UI demo which you can use for simple conversions

In your own code, the Converter class can be used in a number of ways:

  • Simple use: built-in converters
  • Advanced use: custom converters
  • Advanced use: converter instances

...these are detailed below

Simple use: built-in converters

The simplest method is to use one of the 12 built-in static converters:

  • Convert.BinToDec.Convert()
  • Convert.BinToHex.Convert()
  • Convert.BinToOct.Convert()
  • Convert.DecToBin.Convert()
  • Convert.DecToHex.Convert()
  • etc.

This allows all conversion combinations using Binary, Octal, Decimal and Hexadecimal. For example:

// Convert FFFF (hex) to binary:

string binary = Converter.HexToBin.Convert("FFFF");

Advanced use: custom converters

In addition to the built-in static converters you can also perform custom conversion:

// Convert FFFF (hex) to base 5:

string base5 = Converter.Convert(NumberBases.Hexadecimal, 5, "FFFF");

Advanced use: converter instances

Converter instances can also be created instead of using the built-in static converters or the static Converter.Convert() methods (overloaded)

Instances are created using the static Converter.Create() factory methods which have a number of overloads. Once an instance is created, calls can be made to the Convert() method to perform conversions using the number bases specified when creating the converter instance

// base 26 (alphabet based) such as Excel column names --> decimal

Converter fromExcel = Converter.Create(26, NumberingSchemes.AToZ, NumberBases.Decimal,

string columnNumber = fromExcel.Convert("AA");


There are a few limitations to bear in mind:

  • Negative numbers are not supported
  • All converted values are returned as strings
  • The largest value that can be converted is Int64.MaxValue as long is used internally
  • Special character denoting number bases are not supported. For instance, Hexadecimal values are often written as 0xFF01 or &HFF01. This class requires the simpler FF01 notation

Points of Interest

The download includes unit tests (requires NUnit) which, apart from validating the conversions and testing class behaviour, also shows a number of other ways to use the class

The source is liberally commented and the associated documentation file (.CHM) is included

Further development

A couple of future plans:

  • Allow use of custom numbering strings. i.e. user defined symbols to use as digits
  • Support for number bases > 36


  • Version 1.0 - 1st Jan 2007 - Initial version


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

Written By
Architect oo.magic
United Kingdom United Kingdom
Mark Gwilliam is a freelance .Net consultant based in the UK specialising in .Net architecture, design and coding.

He has been working in IT for around 15 years and has worked primarily in the financial sector and is always keen to lead, learn, follow or teach

Comments and Discussions

QuestionMaximum string length Pin
Bhavesh Maniya6-Jul-15 1:47
Bhavesh Maniya6-Jul-15 1:47 
AnswerPlease post a complete code using C# Pin
Reyden Mercado Quijano1-Sep-15 0:53
Reyden Mercado Quijano1-Sep-15 0:53 
QuestionThis Version has no Size Limit Pin
Joe Monnin31-Mar-14 16:07
Joe Monnin31-Mar-14 16:07 
GeneralRe: This Version has no Size Limit Pin
PIEBALDconsult31-Mar-14 17:07
professionalPIEBALDconsult31-Mar-14 17:07 
GeneralRe: This Version has no Size Limit Pin
Joe Monnin3-Apr-15 7:55
Joe Monnin3-Apr-15 7:55 
QuestionCan find nunit.framework Pin
Member 100324516-May-13 7:40
Member 100324516-May-13 7:40 
QuestionAnother Way of Doing the Same Thing Pin
John d. Bartels16-Jan-12 12:43
John d. Bartels16-Jan-12 12:43 
QuestionMerci Pin
petite pomme29-Sep-11 5:21
petite pomme29-Sep-11 5:21 
GeneralDoesn't convert zero Pin
Darchangel27-Mar-09 4:17
Darchangel27-Mar-09 4:17 
GeneralRe: Doesn't convert zero Pin
John d. Bartels16-Jan-12 12:56
John d. Bartels16-Jan-12 12:56 
GeneralThank You Pin
Benjano5-Feb-09 5:43
professionalBenjano5-Feb-09 5:43 
GeneralGreat ... but Pin
mahpet20-Feb-08 10:32
mahpet20-Feb-08 10:32 
GeneralRe: Great ... but Pin
MarkGwilliam21-Feb-08 8:59
MarkGwilliam21-Feb-08 8:59 
GeneralRe: Great ... but Pin
#realJSOP31-Aug-08 1:50
mva#realJSOP31-Aug-08 1:50 
GeneralRe: Great ... but Pin
dzCepheus26-Mar-09 8:57
dzCepheus26-Mar-09 8:57 
GeneralVery useful class Pin
Lieven I29-Oct-07 1:05
Lieven I29-Oct-07 1:05 
GeneralRe: Very useful class Pin
MarkGwilliam29-Oct-07 9:32
MarkGwilliam29-Oct-07 9:32 
GeneralSimilar work Pin
rvdt7-Jan-07 22:20
rvdt7-Jan-07 22:20 
GeneralA sugestion... Pin
Stanciu Vlad23-Dec-06 22:39
Stanciu Vlad23-Dec-06 22:39 
GeneralNice Article Pin
Paul Conrad23-Dec-06 19:07
professionalPaul Conrad23-Dec-06 19:07 

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