Size
The biggest difference between foxes and coyotes are their size. Foxes are usually about 18 to 33 inches long. A coyote measures from about 32 to 37 inches long. A coyote's tail is approximately 16 inches long and a fox's is 12 to about 22 inches long. One way to gauge the size difference between a fox and a coyote is to picture a wolf and a fox. A coyote would be right in the middle in size between those two animals.
Weight
Coyotes are not only longer than foxes, they also weigh more, usually between 20 and 50 lbs. A fox, on the other hand, weighs 6.5 to 24 lbs. Coyotes look more like the size of a medium sized dog.
Color
Foxes can be red, golden, black or gray. Coyotes can range from gray to a dull yellow color. On the back and the neck, the coyote's hair is typically gray.
Speed
If you are lucky to see a coyote or fox on the run, you will quickly be able to distinguish between the two. They are both fast animals but a coyote in a full run can reach speeds of up to 40 miles an hour. While foxes do not run as fast as coyotes, German mammalogist Theodor Haltenorth and Italian FAO biologist H. Roth have reported that the red fox can reach a top speed of 30 miles an hour. A fox can run fast, but can not sustain its speed for as long as the coyote.