C++ Program For Double to String Conversion

Last Updated : 24 Aug, 2026

A double value can be converted into a string when numeric data needs to be stored or processed as text. C++ provides several approaches for this conversion, including to_string(), stringstream, sprintf(), and boost::lexical_cast().

  • to_string() is the simplest standard C++ approach.
  • stringstream and sprintf() provide more control over formatting and precision.

Examples:

Input: 456321.7651234
Output: "456321.765123"

Input: 2332.43
Output: "2332.43"

Methods to Convert Double to String in C++

The conversion can be performed using the following methods:

1. Using to_string()

The std::to_string() function converts a numeric value into its string representation. It is the simplest approach when no special formatting is required.

C++ 
#include <iostream>
#include <string>
using namespace std;

int main()
{
    double n = 456321.7651234;

    // Convert double to string
    string str = to_string(n);

    cout << "String is: " << str;

    return 0;
}

Output
String is: 456321.765123

Explanation

  • to_string() converts the double value into a string.
  • The resulting string can be stored, displayed, or used in further string operations.
  • The default formatting may limit the number of digits shown after the decimal point.

2. Using stringstream

A stringstream or ostringstream can convert a double into a string while also providing formatting options such as precision.

C++ 
#include <iostream>
#include <sstream>
#include <string>
using namespace std;

int main()
{
    double n = 2332.43;
    ostringstream stream;

    // Insert double value into the stream
    stream << n;

    // Get the resulting string
    string str = stream.str();

    cout << "String is: " << str;

    return 0;
}

Output
String is: 2332.43

Explanation

  • ostringstream treats the double value as a stream of characters.
  • The << operator inserts the value into the stream.
  • str() extracts the converted value as a string.

3. Using sprintf()

The sprintf() function converts a double into a C-style character array. It is useful when custom formatting or precision is required.

C++ 
#include <cstdio>
#include <iostream>
using namespace std;

int main()
{
    double n = 1243.3456;
    char str[50];

    // Convert double to a formatted C-style string
    sprintf(str, "%.4f", n);

    cout << "String is: " << str;

    return 0;
}

Output
string is: 1243.345600

Explanation

  • sprintf() formats the double value according to the specified format.
  • %.4f keeps exactly four digits after the decimal point.
  • The result is stored in the character array str.

4. Using boost::lexical_cast()

boost::lexical_cast() converts values between strings and other data types. It requires the Boost library and can be used when Boost is already part of the project.

C++ 
#include <boost/lexical_cast.hpp>
#include <iostream>
#include <string>
using namespace std;

int main()
{
    double n = 432.12;

    // Convert double to string
    string str = boost::lexical_cast<string>(n);

    cout << "String is: " << str;

    return 0;
}

Output
string is:432.12

Explanation

  • boost::lexical_cast<string>() converts the double value into a string.
  • The converted value is stored in str.
  • This approach is useful when the Boost library is already being used in the project.
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