At the time of Noah’s flood, how could all of the animals have fit in the ark?
There are a couple of things we have to keep in mind. First, the ark was simply enormous. We are given the dimensions in Genesis 6:15.
This is how you are to make it: the length of the ark 300 cubits, its breadth 50 cubits, and its height 30 cubits.
A cubit is one and half feet. So whenever you encounter a cubit in Scripture, multiply by 1½ and you’ll get the equivalent length in feet. So the dimensions of the ark were 450 feet long, 75 feet wide and 45 feet high. Or to put it into a perspective we can visualize, the ark was 1½ football fields in length, about half the width of a football field, and taller than a four storey building.
In addition, Noah was to make it with three decks, or levels. All told the storage capacity of the ark was equivalent to 522 standard railroad stock cars, each of which is capable of holding 240 sheep.
The second thing to consider is the number of animals that had to be brought on the ark: one pair of every kind of unclean animal, a male and a female; and seven of every kind of clean animal, three mating pairs plus an extra to be sacrificed at the end of the flood (Gen. 7:2-3). This, of course, excludes marine animals which would not have been necessary to take on the ark, and probably insects as well.
Now, how many different kinds of animals did this involve? Probably far fewer than what we might think. For instance, there were probably not two Great Danes and two dachshunds and two beagles and two Dobermans on the ark. More likely there were two dog-type animals that had the genetic potential to produce all these different varieties in their descendants. Not only this, but they probably also had the genetic potential to produce wolves and coyotes and foxes and dingoes and everything else that is what we might call “dog-like.”
And so on with other kinds of animals.
It is doubtful that there were representatives of all the different species that modern taxonomists have identified. It’s more likely the case that only representatives of each genus, and in some cases of each family, were on the ark, and that they had the genetic potential to produce the great variety of related animals that we see in the world today. There were perhaps fewer than 20,000 individual animals aboard the ark.
Furthermore, it has been estimated that “the median size of all animals on the Ark would most likely have been that of a small rat...” and “only about 11 percent would have been much larger than a sheep.” There would have been plenty of room to accommodate these animals together with the food supplies necessary to feed them.