Setprecision C++ with Examples

A setprecision() is an in-built function defined in iomanip C++ header file. It is used to control the decimal number of output. If the setprecision() is called with n as an argument, it will convert the number with a precision of n argument. 

Note: Using the Setprecision function on int will give output in an integer format. So C++ setprecision is not working on integer datatype.

Syntax

setprecision(argument);

Where the argument is the count of decimal precision.

How to use setprecision in C++?

To use setprecision, You must declare a number, and while printing, use the function and pass the count of the decimal number you want to print in the output as an argument. 

If the number has 4 or 5 decimal points and you want to print 7 or 8 decimal points in the output use, C++ fixed setprecision. The use of fixed setprecision is shown below in the example.

Examples of setprecision in C++

1. Using setprecision on the double data type.

#include <iostream> //header file for cout and fixed

#include <iomanip>  //header file for setprecision   
using namespace std;  
  
int main () {  
  double f =8.38274;  
  cout << setprecision(5) << f << '\n';  
  cout << setprecision(6) << f << '\n';  
  cout << fixed;
  cout << "After using fixed precision" << '\n';
  cout << setprecision(7) << f << '\n';  
  cout << setprecision(9) << f << '\n';  
  return 0;  
} 

Output

8.3827                                                                                                            
8.38274                                                                                                           
After using fixed precision                                                                                       
8.3827400                                                                                                         
8.382740000

2. Using setprecision on the float data type.

#include <iostream> //header file for cout and fixed
#include <iomanip> //header file for setprecision 
using namespace std;  
  
     int main (void)  
     {  
        float  a,b,c;  
        a = 22;  
        b = 7;  
        c = a/b;  
        cout << setprecision (1) << c << endl;  
        cout << setprecision (2) << c << endl;  
        cout << setprecision (3) << c << endl;  
        cout << setprecision (4) << c << endl;  
        cout << setprecision (5) << c << endl; 
        cout << setprecision (10) << c << endl;  
        return 0;  
    }

Output

3                                                                                                                  
3.1                                                                                                                
3.14                                                                                                               
3.143                                                                                                              
3.1429                                                                                                             
3.14285707473754882812

The fixed notation is declared in the C++ iostream header file . To use it, you must include iostream header file in the program. After using fixes precision, you can see the number of an argument passed to the function is a total count of decimal numbers. That means the setprecision function adds zero’s at the end of a number if the total count of numbers after the decimal point is less than passed argument.