Area calculator (square, circle, triangle...)

Area measures a plane figure's surface, always in squared units (cm², m²…). Each figure has its formula:

• Square: side²
• Rectangle: base × height
• Triangle: (base × height) ÷ 2
• Circle: π × radius² (radius = half the diameter)
• Trapezoid: ((major base + minor base) ÷ 2) × height

Step-by-step examples

• Rectangle 5 × 3 = 15
• Triangle base 6, height 4: (6 × 4) ÷ 2 = 12
• Circle radius 5: π × 25 ≈ 78.5

Why a triangle is "half" a rectangle

Any triangle fits exactly in half a rectangle of the same base and height — hence the ÷ 2, as long as the height is the perpendicular distance from base to opposite vertex.

Irregular figures

Split into rectangles and triangles, compute each and add. For cut-outs, subtract the removed part.