Is it possible to tell a dog gender based solely on its size/head/face

2. The Heads of Male Dogs Are Larger

When it comes to physical variations between male and female dogs, the shape of the head is frequently more defining than size. Some breeds of dogs have smaller skulls with more delicate, refined characteristics on the males and larger, blockier heads on the females. For instance, the head of a German shepherd dog breed is supposed to look more feminine in females and more manly in males.