Expansion indicates how much the popcorn will expand when cooked. Its units are litres per kg, meaning how many litres the cooked popcorn may occupy if 1 kg of raw popcorn is cooked. For example, if 1 kg popcorn of 48 expansion is cooked, it will occupy 48 litres after cooking. Higher expansion helps theatres fill more tubs with each kg of popcorn. So higher the expansion, higher the revenue for theatres.