The most common type of pallet is the Euro pallet: 31.5 in wide x 47.24 in long (80 cm x 120 cm). Pallets are also available with a dimension of 40 in x 48 in (1.016 m x 1.219 m). This type of pallet is most commonly used in North America. Another size of pallet that is used is 39.37 in x 47.24 in (1.00 m x 1.200 m), which is most commonly used in Europe and Asia and is actually comparable to the 40 in x 48 in (1.016 m x 1.219 m) pallet.
Number of pallets that fit in a 20ft container
A 20ft container can hold between 10 and 11 pallets (depending on the size and type of cargo on the pallet).
Number of pallets that fit in a 40ft container
A 40ft container can hold between 20 and 24 pallets (depending on the size and type of cargo on the pallet).
The illustration below shows roughly how many pallets the different containers can hold.