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Area formulas
Need a area formulas within reach? Print it for the wall, then hand off to the practice sheets below.
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Reference chart
Area formulas
Rectangle
l × w
8 × 3 = 24 sq cm
Square
s × s
6 × 6 = 36 sq cm
Triangle
b × h ÷ 2
10 × 4 ÷ 2 = 20
Parallelogram
b × h
not the slant
9 × 5 = 45 sq cm
Trapezoid
(a + b) ÷ 2 × h
16 ÷ 2 × 4 = 32
Circle
π × r × r
3.14 × 25 = 78.5
The dashed line is the height, and it is never a slanted side. Area is counted in squares, so the answer is in sq cm or sq in.
What's on this chart
The dashed line is the reason this page is drawn rather than written. "Base × height, never the slant side" is a true sentence and a useless one: a child staring at a parallelogram with three numbers on it needs to be shown which of the three, and reaching for the slant is the most common area mistake there is after mixing area up with perimeter. A dashed line is visibly not an edge, so it cannot be counted as one.
Why this chart helps
Shading does the other half. Every shape here is filled, and the rectangle and square are ruled into unit squares, because area is the inside — it is how many squares fit, which is what "square centimetres" has been trying to tell a child all along. The perimeter chart leaves its shapes empty for exactly the same reason.
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