There is no universal standard for pallets, various sizes and norms like ISO, GMA, Euro and UK pallets are used around the world and by different cargo movers depending on their requirements. The information below should be used as guidance only.
In a 20ft container you can load 11 EUR pallets or 9-10 UK standard pallets
In a 40ft container you can load 23-24 EUR pallets or 20-21 UK standard pallets
In a 13.6m standard trailer you can load 33 EUR pallets or 26 UK standard pallets