The entrance should be even smaller that the overall dimensions. It should have a width of about 9 inches and about 9 inches in height.
Small entrances are beneficial, because they allow minimum light into the boxes and create a more comfortable area for you laying hens. Less light is desirable for improving the production of eggs. Also, the small entrance minimizes the chances of eggs rolling out of the nesting box and discourages chickens from entering the boxes unless they are laying.
Generally, it should be cozy without being tight
To increase the production of eggs and prevent cracked eggs, the nesting boxes should be designed to have a width of 12 inches. The height should be 9 inches and the depth is to be 12 inches.
The chicken nesting box size is very important, however should be relative to the size of hens. These measurements will work for most common backyard chicken breeds. If you are tending to a breed that is particularly large or small, you will need to adjust these dimensions to fit your flock.
size of nest box for chickens | The Scoop from the Coop
These chicken nesting box dimensions help in preventing undesirable behaviors of the chickens, such as scratching the nests, breaking eggs, pooping on the eggs, or not using the nesting boxes at all. When the hens are given more space, they are more likely to scratch materials in the nest, cracking eggs, or to roost in the nest.
Best chicken nest box dimensions? - Walden Effect
After observing our chickens we would agree that the new dimensions of the nesting boxes seem to suit our small flock. We have a dozen chickens total and two breeds: Leghorns and Rhode Island Reds.Dimensions of nesting box for chicken are important factor with respect to the egg laying behavior of hens. These dimensions also play important part to eliminate happenings, like eating eggs, hiding egg & using these nesting as roosts. When you have nesting box with small dimensions you have made good decision for enhanced eggs production.