Regular Expressions 101

Community Patterns

Sanitize percentage input into bare real number


Regular Expression
.NET 7.0 (C#)

^ *([\+\-]?) *(?>([0-9]+)[.,]?([0-9]*)|[.,]?([0-9]+)) *%? *$


Turn "123,456 %" into just "123.456"!

Mainly for use in C# to parse percentage as string into double.

  • Strip away whitespace
  • Replace comma with decimal point
  • Only allow valid numeric input
    • multiple commas or decimal points won't match
      • therefore does not support thousands-grouping, not even spaces, sorry
    • multiple % symbols won't match
    • any character not 0-9, ,, . or % won't match
    • + or - will match, but +- or ± will not, nor will any other operators
  • Using $1$2.$3$4 for substitution spits out a sanitized number with a forced decimal point.

Note: The decimal point is present even when the number input doesn't include any decimals, e.g. for 12% the result will be 12.. You may wish to append a 0 in your code to make it 12.0 - in .NET 4.5 C# the double.Parse and double.TryParse handle the result just fine even without that, but your mileage may vary.

See example on

Submitted by Moravuscz - a year ago