In Year One, children are introduced to the language around mass. They use words like "heavier" and "lighter" to compare mass of objects. They also give the mass of objects using non-unit measures and balance scales. 

Children build on their knowledge of mass in Year Two by beginning to measure in grams and kilograms and read scales. They continue comparing the mass of objects. 

When they reach Year Three, children begin to measure mass in grams and kilograms. They learn to read scales with different sized intervals. 

In Year Four, children begin converting between units of mass. They use their knowledge of 1000g=1kg to do this, thinking about how many whole kg there are. 

Children in Year Five continue converting between metric units of mass using their knowledge of multiplying and dividing by 10, 100 and 1000. They also convert between metric and imperial units.

Time is spent in Year Six consolidating children's knowledge of converting between metric units of mass, including the larger unit of tonnes. Some time is also spent looking at imperial measures of mass.