White-tailed deer can jump almost 8 feet high and can jump a 30-foot distance. In a University of Vermont study, all the deer easily cleared 6 feet, most cleared 7 feet and most didn't try to jump over an 8 foot fence.
The occasional deer has been observed jumping over an 8-foot-high fence from a standstill. Deer can also run at 35 to 40 miles per hour.
Fences that are effective in keeping deer out need to be both high and wide. A 6-foot fence slanting outward at a 45 degree angle is often effective. Another effective option is two 5-foot fences placed 4 feet apart.