Cookbooks
Arduino
Chapter 2. Strings
Finding the length of a string

Arduino:
Finding the length of a string

How to: 

void setup() {
  Serial.begin(9600); // Start the serial communication
  String myString = "Hello, Arduino!"; // Your string here
  int stringLength = myString.length(); // Finding the length of the string
  Serial.print("The length of the string is: ");
  Serial.println(stringLength); // Outputs the length
}

void loop() {
  // Nothing to do here.
}

Sample Output:

The length of the string is: 15

Deep Dive

Back in the day, C programmers used the strlen() function from <string.h>, counting characters until a null-terminator. In Arduino’s world, the String class makes life easier with its built-in length() method. But remember, using String objects can fragment your device’s limited memory over time. An alternative? Use char arrays (C-style strings), which are more memory-friendly but trickier to handle.

For larger projects, always consider memory management. With the length() method, no extra computing is needed—the String object keeps track of its size. Internally, length() is a quick look-up, not a character count. That’s efficient! But, if you’re low on memory, go back to basics with char arrays and manual length calculations, just like the good ol’strlen() days.

See Also

Extracting substringsInterpolating a string