Regular Expression for Decimal or Blank

Question

Sorry for the potentially dumb question but I am trying to pull together a regular expression that will allow:

A number with 1 or 2 numbers before a decimal point, and 0-6 numbers after the decimal point. However I also need to allow the field to be blank if so required.

Valid Examples

0.952321
1.20394
12.12
25
Blank

Invalid Examples

123.45678
1.1234567

Please can anyone help?

Answer 1

^(?:\d{1,2}(?:\.\d{0,6})?)?$

Should do the trick.

\d     matches any digit
{n,m} specifies the number of occurrences
(?: ) creates an anonymous group
^     specifies the start of the string
$               the end of the string
?     means the group is optional

Answer 2

^(?:|\d{1,2}(?:\.\d{0,6})?)$

The part before the pipe matches blank. The part after matches one or two digits optionally followed by a period and up to six digits. The ?: are so we don't use capturing groups unless needed.

Hope this helps!