For medium-size dog breeds, considered a whelping box that is about 28 to 34 inches long by 28 to 34 inches deep. Large dog breeds need whelping boxes that measure about 42 to 45 inches long by 34 to 40 inches deep. Extra-large breeds need boxes at least 48 to 58 inches long by 40 to 48 inches deep.

Can a whelping box be too big?

Many considerations go into setting up the ideal whelping box for your breed of dog. Importantly, the size should be appropriate — large enough for a dam to stretch out with some room to spare — as a box that is too large can cause her great distress.

Do you really need a whelping box?

As the last week of pregnancy approaches, your female dog will often begin looking for a secure and comfortable place to have her litter of puppies. Before this time comes, it is essential to create a whelping box so she becomes comfortable with it and knows this is the preferred place to have her puppies.