Arduino How to Convert int to String Easily

In Arduino, convert an int to a string by using String(yourInt) or the itoa() function to store the result in a char array.

Examples

Input123

Output"123"

Input0

Output"0"

Input-456

Output"-456"

How to Think About It

To convert an integer to a string in Arduino, think about turning the number into readable text. You can use the built-in String() function for a quick conversion or use itoa() to fill a character array with the number's digits as text.

Algorithm

1

Take the integer value you want to convert.

2

Use the <code>String()</code> function or <code>itoa()</code> to convert the integer to a string format.

3

Store or print the resulting string as needed.

Code

arduino

void setup() {
  Serial.begin(9600);
  int number = 123;
  String strNumber = String(number);
  Serial.println(strNumber);
}

void loop() {
  // Nothing here
}

Output

123

Dry Run

Let's trace converting the integer 123 to a string using String()

1

Start with integer

number = 123

2

Convert using String()

strNumber = String(123) -> "123"

3

Print the string

Serial.println("123") outputs 123

Step	Variable	Value
1	number	123
2	strNumber	"123"
3	Serial output	123

Why This Works

Step 1: Using String()

The String() function takes an integer and creates a new string object representing that number.

Step 2: Printing the string

When you print the string, Arduino sends the characters one by one to the serial monitor.

Alternative Approaches

Using itoa() function

arduino

void setup() {
  Serial.begin(9600);
  int number = 123;
  char buffer[10];
  itoa(number, buffer, 10);
  Serial.println(buffer);
}

void loop() {
  // Nothing here
}

This method uses a character array and is more memory efficient than String objects.

Using sprintf() function

arduino

void setup() {
  Serial.begin(9600);
  int number = 123;
  char buffer[10];
  sprintf(buffer, "%d", number);
  Serial.println(buffer);
}

void loop() {
  // Nothing here
}

sprintf() formats the integer into a string, useful for complex formatting but uses more memory.

Complexity: O(n) time, O(n) space

Time Complexity

Conversion time depends on the number of digits (n) in the integer, as each digit is processed.

Space Complexity

Extra space is needed to store the string representation, proportional to the number of digits.

Which Approach is Fastest?

Using itoa() is faster and uses less memory than String(), which creates objects dynamically.

Approach	Time	Space	Best For
String()	O(n)	O(n)	Simple and quick code
itoa()	O(n)	O(n)	Memory-efficient and faster
sprintf()	O(n)	O(n)	Formatted strings, more complex