In this C++ tutorial, you will learn how to compute square root of given number using sqrt() function of cmath, with syntax and examples.

C++ sqrt()

C++ sqrt() computes square root of given number (argument).


The syntax of C++ sqrt() is



xA double, float, long double, or any integral type value.


The return value depends on the type of value passed for parameter x.

The return value of sqrt(x) is

  • double if x is double or integral type.
  • float if x is float.
  • long double if x is long double.

If x is negative, then sqrt() returns nan.

The synopsis of sqrt() function is

double sqrt(double x);
float sqrt(float x);
long double sqrt(long double x);
double sqrt(T x); // for integral type argument values

sqrt() is a function of cmath library. Include cmath library at the start of program, if using sqrt() function.



In this example, we read a value from user into variable x, and find its square root using sqrt() function.

C++ Program

#include <iostream>
using namespace std;

int main() {
    double x;
    cout << "Enter a number : ";
    cin >> x;
    double result = sqrt(x);
    cout << "sqrt(" << x << ") : " << result << endl;


Enter a number : 9
sqrt(9) : 3
Program ended with exit code: 0
Enter a number : 2
sqrt(2) : 1.41421
Program ended with exit code: 0
Enter a number : -2
sqrt(-2) : nan
Program ended with exit code: 0


In this C++ Tutorial, we learned the syntax of C++ sqrt(), and how to use this function to find the square root of given number, with the help of examples.