size of vector data

// vector of pointer to T class 
std::vector<T*> animais;

// add new T instance object , into the animais vector pointer 
animais.pushBack( new T() );
animais.pushBack( new T() );

//  show size in bytes , kbytes , megaBytes 
std::cout << (animais.size() * sizeof(std::vector<T>))<<"bytes" << std::endl;
std::cout << (animais.size() * sizeof(std::vector<pessoa>))/ 1024 <<"kb" << std::endl;
std::cout << (animais.size() * sizeof(std::vector<pessoa>))/ 1048576 <<"mb" << std::endl;

Convert Bytes to KiloBytes, MegaBytes, Gigabytes

1 KB = 1024 B 
1 MB = 1048576 B = 1024 KB 
1 GB = 1073741824 B = 1048576 KB = 1024 MB


So... the formula is 

X KB = NumberOfBytes/1024
X MB = NumberOfBytes/1048576 'or X MB = NumberOfBytes/1024/1024

etc, etc.