sqrt() Function in C

Last Updated : 2 Jul, 2026

The sqrt() function is a predefined function in the <math.h> library that is used to calculate the square root of a given number. It returns the result as a double.

  • Include the <math.h> header file to use the sqrt() function.
  • Use sqrtf() for float values and sqrtl() for long double values.
C 
#include <stdio.h>
#include <math.h>

int main()
{
    double num = 64.0;
    double result = sqrt(num);

    printf("Square root of %.2lf = %.2lf", num, result);

    return 0;
}

Output
Square root of 64.00 = 8.00

Syntax

double sqrt(double x);

Parameters: The sqrt() function accepts one parameter:

  • x – A non-negative number whose square root is to be calculated.

Return Value: The sqrt() function returns:

  • The square root of the given number as a double.
  • NaN (Not a Number) if the input value is negative.

Examples

The following examples demonstrate how to use the sqrt() function in C

Example 1: Program demonstrates how we can calculate the square root of a given number using the sqrt(x) function in C.

C++ 
#include <math.h>
#include <stdio.h>

int main()
{
    // Declare variables to store the input number and its
    // square root
    double number, squareRoot;

    // Prompt the user to enter a number
    printf("Enter a number: ");
    // Read the number entered by the user
    scanf("%lf", &number);

    // Compute the square root of the entered number
    squareRoot = sqrt(number);

    // Print the square root with 2 decimal places
    printf("Square root of %.2lf = %.2lf\n", number,
           squareRoot);

    return 0;
}


Output

Enter a number: 25
Square root of 25.00 = 5.00

Example 2: demonstrates how we can calculate square root of different data types in C.

C 
#include <math.h>
#include <stdio.h>

int main()
{

    // Declare and initialize variables of different types
    // double type variable
    double num1 = 9.0;
    // float type variable
    float num2 = 16.0f;
    // long double type variable
    long double num3 = 25.0l;

    // Compute the square root using the appropriate sqrt
    // function for each type sqrt function for double
    double result1 = sqrt(num1);
    // sqrtf function for float
    float result2 = sqrtf(num2);
    // sqrtl function for long double
    long double result3 = sqrtl(num3);

    // Print the results
    printf("Square root of %.2f is %.2f\n", num1, result1);
    printf("Square root of %.2f is %.2f\n", num2, result2);
    printf("Square root of %.2Lf is %.2Lf\n", num3,
           result3);

    return 0;
}

Output
Square root of 9.00 is 3.00
Square root of 16.00 is 4.00
Square root of 25.00 is 5.00


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