In this tutorial, we will learn how to find the length of a string in C++. Understanding how to find the length of a string is crucial in various programming scenarios, such as data validation, parsing, and manipulation. C++ provides multiple ways to achieve this, and we'll explore the most common and efficient methods.

Understanding String Length in C++

The length of a string refers to the number of characters it contains, including spaces, but not the null terminator character \0 that signifies the end of the string. In C++, strings can be handled using the C-style character arrays or the string class introduced by the Standard Template Library (STL).

Method 1: Using the strlen() Function

When dealing with C-style strings, which are arrays of characters terminated by a null character \0, the standard approach to finding the string's length is to use the strlen() function. This function is part of the <cstring> header (or <string.h> in C) and calculates the length by counting characters until it reaches the null terminator.


#include <iostream>
#include <cstring> // For strlen()

int main() {
    char str[] = "Explore C++";
    int length = strlen(str);
    std::cout << "The string's length is: " << length << std::endl;
    return 0;


The string's length is: 11

This method is exclusive to C-style strings and incompatible with the STL string class.

Method 2: Using the string Class

The C++ string class, part of the STL, provides a modern and safer alternative to C-style strings. It comes with two member functions, .length() and .size(), which returns the string's length.


#include <iostream>
#include <string> // For the string class

int main() {
    std::string str = "Discover C++";
    // Using length()
    std::cout << "The string's length is: " << str.length() << std::endl;
    // Alternatively, using size()
    std::string myString = "C++ Programming Insights";
    std::cout << "Length using size(): " << myString.size() << std::endl;
    return 0;


The string's length is: 12
Length using size(): 24

Choosing the Right Method

  • For C-style strings: Use strlen() when dealing with legacy C code or when interacting with C libraries.
  • For STL strings: Use the .length() or .size() methods for safer and more convenient string handling.


Understanding how to find the length of a string accurately is crucial for effective string manipulation in C++. This tutorial covered the use of the strlen() function for C-style strings and the length() or size() methods for strings managed by the C++ STL. With this knowledge, you can efficiently handle strings in your C++ programs, whether working with traditional C-style strings or the more modern STL string class.

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