How do I print a double value with full precision using cout in C++?

The output stream cout allows using manipulators that you can use to set the precision directly on cout and use the fixed format specifier. To get the full precision of a double, you can use the limits library. For example,

Example

#include<iostream>
#include <limits>
using namespace std;
int main() {
    // Get numeric limits of double
    typedef std::numeric_limits< double > dbl;
    double PI = 3.14159265358979;
    cout.precision(dbl::max_digits10);
    cout << "Pi: " << fixed << PI << endl;
    return 0;
}

Output

This will give the output −

3.14159265358979