iMac 27" box dimensions

Can't tell you the weight but it's a little over 31 pounds.

The size is:

2 ft tall
2 ft 6 1/4 inches wide
9 3/4 inches deep

The above dimensions are the apple box and don't include the shippers box.

The iMac itself:


27-inch iMac

Height:
20.4 inches (51.7 cm)
Width:
25.6 inches (65.0 cm)
Depth:
8.15 inches (20.7 cm)
Weight:
30.5 pounds (13.8 kg)

You can check more about it here