How large is the average adult porcupine?

Porcupines grow to be 25 to 36-inches long with an 8 to 10-inch tail. Porcupines weigh up to 35-pounds when adults. Porcupines live on a diet of leaves, herbs, and green plants. North American porcupines climb trees to forage for good, while African porcupines remain on the ground.