Central principles

Measurement units

Fundamental to the idea of measuring is the use of a ‘unit’. The use of non-standard units to introduce to pupils the idea of measuring in units is a well-established tradition in primary-school mathematics teaching. For example, they might measure the length of items of furniture in spans, the length of a wall in cubits (a cubit is the length of your forearm), the mass of a book in conkers, the capacity of a container in egg-cups.

Remember to introduce the idea of measuring in units via non-standard units that are familiar and appropriately sized, and use these experiences to establish the need for a standard unit.

Many adults make use of non-standard units of length in everyday life, especially, for example, when making rough-and-ready measurements for practical jobs around the house and garden. The value of this approach is that children get experience of the idea of measuring in units through familiar, unthreatening objects first, rather than going straight into the use of mysterious things called millilitres and grams, and so on.

Also, it is often the case that the non-standard unit is a more appropriate size of unit for early measuring experiences. For example, most of the things around the classroom the pupils might want to weigh will have a mass of several hundred grams. The gram is a very small mass for practical purposes to begin with, and the kilogram is far too large, conkers and glue-sticks are much more appropriate sizes of units for measuring mass in the early stages. Eventually, of course, we must learn that there is a need for a standard unit. The experience of working with non-standard units often makes this need explicit, as, for example, when two pupils measure the length of the hall in paces and get different answers.