How to check numeric strings in Flutter and Dart

Last updated on February 14, 2023 A Goodman Loading... Post a comment

A numeric string is a string that represents a number. Numeric strings can contain digits (0-9) and may also include a decimal point, a minus sign (for negative numbers), and an optional exponential notation (for very large or small numbers).

In simple words, a numeric string is just a number in string format.

Examples of valid numeric strings:


To check whether a string is a numeric string, you can use the double.tryParse() method. If the return equals null, then the input is not a numeric string; otherwise, it is.

if(double.tryParse(String input) == null){
   print('The input is not a numeric string');
} else {
   print('Yes, it is a numeric string');


The code:

void main() {
  var a = '-33.230393399';
  var b = 'ABC123';

  if (double.tryParse(a) != null) {
    print('a is a numeric string');
  } else {
    print('a is NOT a numeric string');

  if (double.tryParse(b) != null) {
    print('b is a numeric string');
  } else {
    print('b is NOT a numeric string');


a is a numeric string
b is NOT a numeric string

Hope this helps. Further reading:

You can also take a tour around our Flutter topic page and Dart topic page to see the latest tutorials and examples.

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