.NET convert number to string representation (1 to one, 2 to two, etc...)

Question

Is there a built in method in .NET to convert a number to the string representation of the number? For example, 1 becomes one, 2 becomes two, etc.

Answer 1

Here is a more complete/improved solution based on a couple ideas also posted here. Includes grammar/hyphen fixes, and optional capitalization, long support, support for zero, and yet still very succinct (VB.Net):

Function NumberToCapitalizedWords(ByVal n As Long) As String
    Return New System.Globalization.CultureInfo("en-US", False).TextInfo.ToTitleCase(NumberToWords(n))
End Function

Function NumberToWords(ByVal n As Long) As String
    Return LTrim(NumberToWords(n, False, False))
End Function

Function NumberToWords(ByVal n As Long, ByVal recursed As Boolean, ByVal iesLast As Boolean) As String
    If (n < 0) Then
        Return "negative" + NumberToWords(-n, False, False)
    ElseIf (n = 0) Then
        If recursed Then
            Return ""
        End If
        Return "zero"
    ElseIf (n < 20) Then
        Return If(iesLast, "-", " ") + New String() {"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"}(n - 1)
    ElseIf (n < 100) Then
        Return " " + New String() {"twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"}(n \ 10 - 2) + NumberToWords(n Mod 10, True, True)
    ElseIf (n < 1000) Then

        Return NumberToWords(n \ 100, True, False) + " hundred" + NumberToWords(n Mod 100, True, False)
    Else
        Dim log1000 As Integer = Math.Floor(Math.Log(n, 1000))
        Return NumberToWords(n \ PowerNoFloat(1000, log1000), True, False) + " " + New String() {"thousand", "million", "billion", "trillion", "quadrillion", "quintillion"}(log1000 - 1) + NumberToWords(n Mod PowerNoFloat(1000, log1000), True, False)
    End If

End Function

Function PowerNoFloat(ByRef base As Long, ByRef power As Integer) As Long
    If power < 0 Then
        Return 0
    End If
    Dim result As Long = 1
    For i As Integer = 1 To power
        result *= base
    Next
    Return result
End Function

Answer 2

Ah, there may not be a class to do this, but there was a code golf question which I provided a C# example for:

Code Golf: Number to Words

However, it's not the easiest to read and it only goes up to decimal.MaxValue, so I've written a new version that will go as high as you need to.

I couldn't find any information regarding values higher than vigintillions, but if you append the values to the thou[] array, you can continue going up as far as you like. It still doesn't support fractions, but I'm thinking about adding that at some point.

    static string NumericStringToWords(string NumericValue)
    {
        if ("0" == NumericValue) return "zero";

        string[] units = { "one", "two", "three", "four", "five", 
                           "six", "seven", "eight", "nine" };

        string[] teens = { "eleven", "twelve", "thirteen", "four", "fifteen", 
                           "sixteen", "seventeen", "eighteen", "nineteen" };

        string[] tens = { "ten", "twenty", "thirty", "forty", "fifty", 
                          "sixty", "seventy", "eighty", "ninety" };

        string[] thou = { "thousand", "million", "billion", "trillion", 
                          "quadrillion", "quintillion", "sextillion", 
                          "septillion", "octillion", "nonillion", "decillion", 
                          "udecillion", "duodecillion", "tredecillion", 
                          "quattuordecillion", "quindecillion", "sexdecillion", 
                          "septendecillion", "octodecillion", "novemdecillion", 
                          "vigintillion" };

        string sign = String.Empty;
        if ("-" == NumericValue.Substring(0, 1))
        {
            sign = "minus ";
            NumericValue = NumericValue.Substring(1);
        }

        int maxLen = thou.Length * 3;
        int actLen = NumericValue.Length;
        if(actLen > maxLen)
            throw new InvalidCastException(String.Format("{0} digit number specified exceeds the maximum length of {1} digits.  To evaluate this number, you must first expand the thou[] array.", actLen, maxLen));

        //Make sure that the value passed in is indeed numeric... we parse the entire string
        //rather than just cast to a numeric type to allow us to handle large number types passed
        //in as a string.  Otherwise, we're limited to the standard data type sizes.
        int n; //We don't care about n, but int.TryParse requires it
        if (!NumericValue.All(c => int.TryParse(c.ToString(), out n)))
            throw new InvalidCastException();

        string fraction = String.Empty;
        if (NumericValue.Contains("."))
        {
            string[] split = NumericValue.Split('.');
            NumericValue = split[0];
            fraction = split[1];
        }

        StringBuilder word = new StringBuilder();
        ulong loopCount = 0;

        while (0 < NumericValue.Length)
        {
            int startPos = Math.Max(0, NumericValue.Length - 3);
            string crntBlock = NumericValue.Substring(startPos);
            if (0 < crntBlock.Length)
            {
                //Grab the hundreds tens & units for the current block
                int h = crntBlock.Length > 2 ? int.Parse(crntBlock[crntBlock.Length - 3].ToString()) : 0;
                int t = crntBlock.Length > 1 ? int.Parse(crntBlock[crntBlock.Length - 2].ToString()) : 0;
                int u = crntBlock.Length > 0 ? int.Parse(crntBlock[crntBlock.Length - 1].ToString()) : 0;

                StringBuilder thisBlock = new StringBuilder();

                if (0 < u)
                    thisBlock.Append(1 == t? teens[u - 1] : units[u - 1]);

                if (1 != t)
                {
                    if (1 < t && 0 < u) thisBlock.Insert(0, "-");
                    if (0 < t) thisBlock.Insert(0, tens[t - 1]);
                }

                if (0 < h)
                {
                    if (t > 0 | u > 0) thisBlock.Insert(0, " and ");
                    thisBlock.Insert(0, String.Format("{0} hundred", units[h - 1]));
                }

                //Check to see if we've got any data left and add
                //appropriate word separator ("and" or ",")
                bool MoreLeft = 3 < NumericValue.Length;
                if (MoreLeft && (0 == h) && (0 == loopCount))
                    thisBlock.Insert(0, " and ");
                else if (MoreLeft)
                    thisBlock.Insert(0, String.Format(" {0}, ", thou[loopCount]));

                word.Insert(0, thisBlock);
            }

            //Remove the block we just evaluated from the 
            //input string for the next loop
            NumericValue = NumericValue.Substring(0, startPos);

            loopCount++;
        }
        return word.Insert(0, sign).ToString();
    }

I tested it using Decimal.MaxValue appended to itself to generate a large number of:

seven octodecillion, nine hundred and twenty-two septendecillion, eight hundred and sixteen sexdecillion, two hundred and fifty-one quindecillion, four hundred and twenty-six quattuordecillion, four hundred and thirty-three tredecillion, seven hundred and fifty-nine duodecillion, three hundred and fifty-four udecillion, three hundred and ninety-five decillion, thirty-three nonillion, five hundred and seventy-nine octillion, two hundred and twenty-eight septillion, one hundred and sixty-two sextillion, five hundred and four quintillion, two hundred and sixty-four quadrillion, three hundred and thirty-seven trillion, five hundred and ninety-three billion, five hundred and forty-three million, nine hundred and fifty- thousand, three hundred and thirty-five

Answer 3

Another naasking, version in VB.NET if any one is interested! Had to use the floor function to round properly..

 Public Function NumberToText(n As Integer) As String
        Dim a As String() = {"One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"}
        Dim tens As String() = {"Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy",
         "Eighty", "Ninety"}

        If (n < 0) Then
            Return "Minus " + NumberToText(-n)
        ElseIf (n = 0) Then
            Return ""
        ElseIf (n <= 19) Then
            Return a(n - 1) + " "
        ElseIf (n <= 99) Then
            Return tens(Math.Floor(n / 10) - 2) + " " + NumberToText(n Mod 10)
        ElseIf (n <= 199) Then
            Return "One Hundred " + NumberToText(n Mod 100)
        ElseIf (n <= 999) Then
            Return NumberToText(Math.Floor(n / 100)) + "Hundreds " + NumberToText(n Mod 100)
        ElseIf (n <= 1999) Then
            Return "One Thousand " + NumberToText(n Mod 1000)
        ElseIf (n <= 999999) Then
            Return NumberToText(Math.Floor(n / 1000)) + "Thousands " + NumberToText(n Mod 1000)
        ElseIf (n <= 1999999) Then
            Return "One Million " + NumberToText(n Mod 1000000)
        ElseIf (n <= 999999999) Then
            Return NumberToText(Math.Floor(n / 1000000)) + "Millions " + NumberToText(n Mod 1000000)
        ElseIf (n <= 1999999999) Then
            Return "One Billion " + NumberToText(n Mod 1000000000)
        Else
            Return NumberToText(Math.Floor(n / 1000000000)) + "Billions " + NumberToText(n Mod 1000000000)
        End If

    End Function

Answer 4

Here's my refined version of the first answer. I hope it's useful.

/// <summary>
/// Converts an <see cref="int"/> to its textual representation
/// </summary>
/// <param name="num">
/// The number to convert to text
/// </param>
/// <returns>
/// A textual representation of the given number
/// </returns>
public static string ToText(this int num)
{
    StringBuilder result;

    if (num < 0)
    {
        return string.Format("Minus {0}", ToText(-num));
    }

    if (num == 0)
    {
        return "Zero";
    }

    if (num <= 19)
    {
        var oneToNineteen = new[]
        {
            "One",
            "Two",
            "Three",
            "Four",
            "Five",
            "Six",
            "Seven",
            "Eight",
            "Nine",
            "Ten",
            "Eleven",
            "Twelve",
            "Thirteen",
            "Fourteen",
            "Fifteen",
            "Sixteen",
            "Seventeen",
            "Eighteen",
            "Nineteen"
        };

        return oneToNineteen[num - 1];
    }

    if (num <= 99)
    {
        result = new StringBuilder();

        var multiplesOfTen = new[]
        {
            "Twenty",
            "Thirty",
            "Forty",
            "Fifty",
            "Sixty",
            "Seventy",
            "Eighty",
            "Ninety"
        };

        result.Append(multiplesOfTen[(num / 10) - 2]);

        if (num % 10 != 0)
        {
            result.Append(" ");
            result.Append(ToText(num % 10));
        }

        return result.ToString();
    }

    if (num == 100)
    {
        return "One Hundred";
    }

    if (num <= 199)
    {
        return string.Format("One Hundred and {0}", ToText(num % 100));
    }

    if (num <= 999)
    {
        result = new StringBuilder((num / 100).ToText());
        result.Append(" Hundred");
        if (num % 100 != 0)
        {
            result.Append(" and ");
            result.Append((num % 100).ToText());
        }

        return result.ToString();
    }

    if (num <= 999999)
    {
        result = new StringBuilder((num / 1000).ToText());
        result.Append(" Thousand");
        if (num % 1000 != 0)
        {
            switch ((num % 1000) < 100)
            {
                case true:
                    result.Append(" and ");
                    break;
                case false:
                    result.Append(", ");
                    break;
            }

            result.Append((num % 1000).ToText());
        }

        return result.ToString();
    }

    if (num <= 999999999)
    {
        result = new StringBuilder((num / 1000000).ToText());
        result.Append(" Million");
        if (num % 1000000 != 0)
        {
            switch ((num % 1000000) < 100)
            {
                case true:
                    result.Append(" and ");
                    break;
                case false:
                    result.Append(", ");
                    break;
            }

            result.Append((num % 1000000).ToText());
        }

        return result.ToString();
    }

    result = new StringBuilder((num / 1000000000).ToText());
    result.Append(" Billion");
    if (num % 1000000000 != 0)
    {
        switch ((num % 1000000000) < 100)
        {
            case true:
                result.Append(" and ");
                break;
            case false:
                result.Append(", ");
                break;
        }

        result.Append((num % 1000000000).ToText());
    }

    return result.ToString();
}

Answer 5

Here is the modified code I used:

//Wrapper class for NumberToText(int n) to account for single zero parameter.
public static string ConvertToStringRepresentation(long number)
{
    string result = null;

    if (number == 0)
    {
        result = "Zero";
    }
    else
    {
        result = NumberToText(number);
    }

    return result;
}

//Found at http://www.dotnet2themax.com/blogs/fbalena/PermaLink,guid,cdceca73-08cd-4c15-aef7-0f9c8096e20a.aspx.
//Modifications from original source:
//  Changed parameter type from int to long.
//  Changed labels to be singulars instead of plurals (Billions to Billion, Millions to Million, etc.).
private static string NumberToText(long n)
{
    if (n < 0)
        return "Minus " + NumberToText(-n);
    else if (n == 0)
        return "";
    else if (n <= 19)
        return new string[] {"One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", 
                                "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", 
                                "Seventeen", "Eighteen", "Nineteen"}[n - 1] + " ";
    else if (n <= 99)
        return new string[] {"Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", 
                                "Eighty", "Ninety"}[n / 10 - 2] + " " + NumberToText(n % 10);
    else if (n <= 199)
        return "One Hundred " + NumberToText(n % 100);
    else if (n <= 999)
        return NumberToText(n / 100) + "Hundred " + NumberToText(n % 100);
    else if (n <= 1999)
        return "One Thousand " + NumberToText(n % 1000);
    else if (n <= 999999)
        return NumberToText(n / 1000) + "Thousand " + NumberToText(n % 1000);
    else if (n <= 1999999)
        return "One Million " + NumberToText(n % 1000000);
    else if (n <= 999999999)
        return NumberToText(n / 1000000) + "Million " + NumberToText(n % 1000000);
    else if (n <= 1999999999)
        return "One Billion " + NumberToText(n % 1000000000);
    else
        return NumberToText(n / 1000000000) + "Billion " + NumberToText(n % 1000000000);
}

Answer 6

There's no built in solution in .net, but there are good libraries around. The best currently is definitely Humanizr:

Console.WriteLine(794663.ToWords()); // => seven hundred and ninety-four thousand six hundred and sixty-three

It also supports ordinal, and roman representations:

Console.WriteLine(794663.ToOrdinalWords()); // => seven hundred and ninety-four thousand six hundred and sixty third
Console.WriteLine(794.ToRoman()); // => DCCXCIV

---

Humanizr also has a wide range of tools regarding string, DateTime, TimeSpan and so forth.

Console.WriteLine(794.Seconds().Humanize().Underscore().Hyphenate()); // => 13-minutes

Answer 7

Based on Ryan Emerle's solution, this adds dashes at the correct locations, does not include trailing spaces, does not pluralize numbers, and properly handles an input of zero (0):

public static string ToText(long n) {
    return _toText(n, true);
}
private static string _toText(long n, bool isFirst = false) {
    string result;
    if(isFirst && n == 0) {
        result = "Zero";
    } else if(n < 0) {
        result = "Negative " + _toText(-n);
    } else if(n == 0) {
        result = "";
    } else if(n <= 9) {
        result = new[] { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine" }[n - 1] + " ";
    } else if(n <= 19) {
        result = new[] { "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen" }[n - 10] + (isFirst ? null : " ");
    } else if(n <= 99) {
        result = new[] { "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety" }[n / 10 - 2] + (n % 10 > 0 ? "-" + _toText(n % 10) : null);
    } else if(n <= 999) {
        result = _toText(n / 100) + "Hundred " + _toText(n % 100);
    } else if(n <= 999999) {
        result = _toText(n / 1000) + "Thousand " + _toText(n % 1000);
    } else if(n <= 999999999) {
        result = _toText(n / 1000000) + "Million " + _toText(n % 1000000);
    } else {
        result = _toText(n / 1000000000) + "Billion " + _toText(n % 1000000000);
    }
    if(isFirst) {
        result = result.Trim();
    }
    return result;
}

Answer 8

public string IntToString(int number)//nobody really uses negative numbers
{
    if(number == 0)
        return "zero";
    else
        if(number == 1)
            return "one";
        .......
        else
            if(number == 2147483647)
                return "two billion one hundred forty seven million four hundred eighty three thousand six hundred forty seven";
}

Answer 9

A conversion from integer to long form English... I could write that ;-) is a pretty good article on the topic:

using System;

public class NumberToEnglish {
    private static string[] onesMapping =
        new string[] {
            "Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine",
            "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"
        };
    private static string[] tensMapping =
        new string[] {
            "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"
        };
    private static string[] groupMapping =
        new string[] {
            "Hundred", "Thousand", "Million", "Billion", "Trillion"
        };

    private static void Main(string[] args) {
        Console.WriteLine(EnglishFromNumber(long.Parse(args[0])));
    }

    private static string EnglishFromNumber(int number) {
        return EnglishFromNumber((long) number);
    }

    private static string EnglishFromNumber(long number) {
        if ( number == 0 ) {
            return onesMapping[number];
        }

        string sign = "Positive";
        if ( number < 0 ) {
            sign = "Negative";
            number = Math.Abs(number);
        }

        string retVal = null;
        int group = 0;
        while(number > 0) {
            int numberToProcess = (int) (number % 1000);
            number = number / 1000;

            string groupDescription = ProcessGroup(numberToProcess);
            if ( groupDescription != null ) {
                if ( group > 0 ) {
                    retVal = groupMapping[group] + " " + retVal;
                }
                retVal = groupDescription + " " + retVal;
            }

            group++;
        }

        return sign + " " + retVal;
    }

    private static string ProcessGroup(int number) {
        int tens = number % 100;
        int hundreds = number / 100;

        string retVal = null;
        if ( hundreds > 0 ) {
            retVal = onesMapping[hundreds] + " " + groupMapping[0];
        }
        if ( tens > 0 ) {
            if ( tens < 20 ) {
                retVal += ((retVal != null) ? " " : "") + onesMapping[tens];
            } else {
                int ones = tens % 10;
                tens = (tens / 10) - 2; // 20's offset

                retVal += ((retVal != null) ? " " : "") + tensMapping[tens];

                if ( ones > 0 ) {
                    retVal += ((retVal != null) ? " " : "") + onesMapping[ones];
                }
            }
        }

        return retVal;
    }
}

Answer 10

This thread was a great help. I like Ryan Emerle's solution the best for its clarity. Here's my version which I think makes the structure clear as day:

public static class Number
{
    static string[] first =
    {
        "Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine",
        "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen",
        "Seventeen", "Eighteen", "Nineteen"
    };
    static string[] tens =
    {
        "Twenty", "Thirty", "Fourty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety",
    };

    /// <summary>
    /// Converts the given number to an english sentence.
    /// </summary>
    /// <param name="n">The number to convert.</param>
    /// <returns>The string representation of the number.</returns>
    public static string ToSentence(int n)
    {
        return n == 0 ? first[n] : Step(n);
    }
    // traverse the number recursively
    public static string Step(int n)
    {
        return n < 0            ? "Minus " + Step(-n):
               n == 0           ? "":
               n <= 19          ? first[n]:
               n <= 99          ? tens[n / 10 - 2] + " " + Step(n % 10):
               n <= 199         ? "One Hundred " + Step(n % 100):
               n <= 999         ? Step(n / 100) + "Hundred " + Step(n % 100):
               n <= 1999        ? "One Thousand " + Step(n % 1000):
               n <= 999999      ? Step(n / 1000) + "Thousand " + Step(n % 1000):
               n <= 1999999     ? "One Million " + Step(n % 1000000):
               n <= 999999999   ? Step(n / 1000000) + "Million " + Step(n % 1000000):
               n <= 1999999999  ? "One Billion " + Step(n % 1000000000):
                                  Step(n / 1000000000) + "Billion " + Step(n % 1000000000);
    }
}

Answer 11

I've always been a fan of the recursive method

  public static string NumberToText( int n)
  {
   if ( n < 0 )
      return "Minus " + NumberToText(-n);
   else if ( n == 0 )
      return "";
   else if ( n <= 19 )
      return new string[] {"One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", 
         "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", 
         "Seventeen", "Eighteen", "Nineteen"}[n-1] + " ";
   else if ( n <= 99 )
      return new string[] {"Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", 
         "Eighty", "Ninety"}[n / 10 - 2] + " " + NumberToText(n % 10);
   else if ( n <= 199 )
      return "One Hundred " + NumberToText(n % 100);
   else if ( n <= 999 )
      return NumberToText(n / 100) + "Hundreds " + NumberToText(n % 100);
   else if ( n <= 1999 )
      return "One Thousand " + NumberToText(n % 1000);
   else if ( n <= 999999 )
      return NumberToText(n / 1000) + "Thousands " + NumberToText(n % 1000);
   else if ( n <= 1999999 )
      return "One Million " + NumberToText(n % 1000000);
   else if ( n <= 999999999)
      return NumberToText(n / 1000000) + "Millions " + NumberToText(n % 1000000);
   else if ( n <= 1999999999 )
      return "One Billion " + NumberToText(n % 1000000000);
   else 
      return NumberToText(n / 1000000000) + "Billions " + NumberToText(n % 1000000000);
}

Source