When compared with the number on roll it can show the number of places that are surplus or the extra places required in a school. When divided by the number of year groups it can be used to show the admission number that can generally be accommodated.
For primary schools, the number and size of spaces designated as classbases calculates the net capacity.
'Rooms used to teach a group of children for at least 80% of their learning' defines a classbase. For secondary schools net capacity is based on the number, size and type of teaching spaces and the age range of the school.