It is called the "Foot Rule".

You start by determining the total number of feet (as in those at the end of the legs, not the kind made up by inches).

Then you divide that total by the number of feet belonging to the person(s) or dog(s) in question. This is how it works:
You and husband share your bed with 1 dog.
You and your husband total 4 feet and the dog also has 4 feet.
That is a total of 8 feet.
The dog has 4 out of 8 feet or 50%, therefore, the dog gets 50% of the bed.

You could work this in reverse as well.
You have 2 out of 8 feet or 25% and so does your husband, so each of you gets 25% and the dog gets 50%.
Now I have 5 dogs. At 4 feet per dog, that is 20 feet. Add to that my 2 feet and we have a total of 22 feet in the bed.
I have 2 out of 22 feet which is 1/11th or 9.1% of the bed.
The dogs, since they share a total of 20 of 22 feet, get 10/11ths or 90.9% of the bed.
Simple isn't it?!

Once I figured out my percent of the bed space, the next step was to work out the exact area that I am entitled to.
My bed is a California King which is approximately 6 ft x 7 ft.

Here is the math:
6 ft x 7 ft = 42 square feet
42 square feet = 6048 square inches
9.1% of 6048 = 550 square inches
550 square inches = 45.8 total inches
45.8 inches = 3.8 total feet

In order to determine the exact size of my bed space, I needed to know the percentage of length to width - this comes out to 54% long to 46% wide.
When I apply these percentages to my spot:
550 square inches x 54% = 297 square inches
50 square inches x 46% = 253 square inches
297 square inches = 24.7 inches
253 square inches = 21.1 inches
24.7 inches = 2.1 feet
21.1 inches = 1.8 feet

Now that the math is all done, the figures show that the dimensions of my part of the bed are 2.1 feet by 1.8 feet or in other words: