If you need more precision in your calculations, you can use this library for big nums. Its simple and easy to start and created in C++ with template classes.
#include <ttmath/ttmath.h>
#include <iostream>
int main()
{
// Big<exponent, mantissa>
ttmath::Big<1,2> a,b,c;
a = "1234.3323454";
b = "3456.1234534";
c = a*b;
std::cout << c << std::endl;
}
solved Is there any variable like BigInteger, but as floating point?