In this C++ tutorial, you will learn how to find absolute value of given number using fabs() function of cmath, with syntax and examples.

C++ fabs()

C++ fabs() returns absolute value of given argument.


The syntax of C++ fabs() is



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


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

The return value of fabs(x) is

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

The synopsis of fabs() function is

double fabs(double x);
float fabs(float x);
long double fabs(long double x);
double fabs(T x); // for integral type argument value

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



In this example, we read a value from user into variable x, and find the absolute value of x using fabs() function.

C++ Program

#include <iostream>
using namespace std;

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


Enter a value : -52
fabs(-52) : 52
Program ended with exit code: 0


Absolute value of a positive number is itself.

Enter a value : 25
fabs(25) : 25
Program ended with exit code: 0


In this C++ Tutorial, we learned the syntax of C++ fabs(), and how to use this function to find the absolute of a value, with the help of examples.