It would be 8.5" by I0.5" if it were square... I added more pics w/ measuring tape, hope they help! ツ. Also added pic of back of picture (so ya know its the original?) I don't know, made sence at the time...
Great shadowing job! That's the one thing most people have the most trouble with! A lot of people can't even draw because of shadowing! That's why I was asking how long did it take you to draw!