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Prints data to the serial port as human-readable ASCII text. This command can take many forms. Numbers are printed using an ASCII character for each digit. Floats are similarly printed as ASCII digits, defaulting to two decimal places. Bytes are sent as a single character. Characters and strings are sent as is. For example-

  • Serial.print(78) gives "78"

  • Serial.print(1.23456) gives "1.23"

  • Serial.print('N') gives "N"

  • Serial.print("Hello world.") gives "Hello world."

An optional second parameter specifies the base (format) to use; permitted values are BIN(binary, or base 2), OCT(octal, or base 8), DEC(decimal, or base 10), HEX(hexadecimal, or base 16). For floating point numbers, this parameter specifies the number of decimal places to use. For example-

  • Serial.print(78, BIN) gives "1001110"

  • Serial.print(78, OCT) gives "116"

  • Serial.print(78, DEC) gives "78"

  • Serial.print(78, HEX) gives "4E"

  • Serial.print(1.23456, 0) gives "1"

  • Serial.print(1.23456, 2) gives "1.23"

  • Serial.print(1.23456, 4) gives "1.2345"

You can pass flash-memory based strings to Serial.print() by wrapping them with F(). For example:

Serial.print(F("Hello World"))

To send data without conversion to its representation as characters, use Serial.write().


Serial.print(val, format)


Serial: serial port object. See the list of available serial ports for each board on the Serial main page.
val: the value to print. Allowed data types: any data type.


print() returns the number of bytes written, though reading that number is optional. Data type: size_t.

Example Code

  Uses a for loop to print numbers in various formats.
void setup() {
  Serial.begin(9600); // open the serial port at 9600 bps:

void loop() {
  // print labels
  Serial.print("NO FORMAT");  // prints a label
  Serial.print("\t");         // prints a tab




  Serial.println();        // carriage return after the last label

  for (int x = 0; x < 64; x++) { // only part of the ASCII chart, change to suit
    // print it out in many formats:
    Serial.print(x);       // print as an ASCII-encoded decimal - same as "DEC"
    Serial.print("\t\t");  // prints two tabs to accomodate the label lenght

    Serial.print(x, DEC);  // print as an ASCII-encoded decimal
    Serial.print("\t");    // prints a tab

    Serial.print(x, HEX);  // print as an ASCII-encoded hexadecimal
    Serial.print("\t");    // prints a tab

    Serial.print(x, OCT);  // print as an ASCII-encoded octal
    Serial.print("\t");    // prints a tab

    Serial.println(x, BIN);  // print as an ASCII-encoded binary
    // then adds the carriage return with "println"
    delay(200);            // delay 200 milliseconds
  Serial.println();        // prints another carriage return

Notes and Warnings

For information on the asyncronicity of Serial.print(), see the Notes and Warnings section of the Serial.write() reference page.