A man in Surrey, England performed a slightly usual experiment with two South American tarantulas, a recently deceased 16-year old Goliath Birdeater and her much smaller counterpart a dwarf Pumpkin Patch. Stretching the legs of the dead Goliath out on a plate, the man was able to show the massive size difference between the two arachnids.
Both are fully grown adult females. The Goliath in this was recently deceased, and 16 years old when she died. One of the few chances you get to actually stretch these spiders out and get a true idea of their size, just under 11 inches. The Pumpkin Patch tarantula is around an inch and a half across.