A mat covers part of the floor. Its area tells us how much surface it covers. Its perimeter tells us the distance around the edge. These measurements answer different questions. To measure area fairly, cover the surface with equal squares without gaps or overlaps.

A square centimetre, written cm², is the area of a square with sides 1 cm long. A square metre, written m², is the area of a square with sides 1 m long. The small raised 2 means square. Use cm² for a small card and m² for a classroom floor. Different-sized counters would give different counts, so we use standard units.

For a rectangle on a square grid, count the squares in one row and the number of rows. Multiply these counts to find the total. This works because every row has the same number of equal squares. For a shape with missing parts, count row by row or subtract the missing squares.

A 6 m by 3 m rectangular floor can be covered with 6 rows of 3 one-square-metre tiles, so its area is 18 m². A 1 m² square contains 100 rows of 100 cm² squares, so it is much larger than 100 cm². You do not need to convert between cm² and m² in this lesson.

An irregular shape may cover whole squares and parts of squares. Count all whole squares, then combine parts that make approximately one whole. Two exact half-squares make one square. Say approximately when you estimate curved edges. Use the same grid size when you compare shapes.

If one shape covers 14 cm² and another covers 11 cm², the first has the greater area by 3 cm². For a nearest-whole-unit estimate, 12 and a quarter cm² rounds to 12 cm²; 12 and three quarters cm² rounds to 13 cm². Explain how you treated the partial squares.

Cut a paper shape into pieces and rearrange every piece without gaps or overlaps. The covered area stays the same. This is conservation of area. A shape can look longer or have a different perimeter while its area remains unchanged.