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Numbers · geometry · trapezoidArea of a trapezoid — formula and calculator

Work out the area of a trapezoid with the formula S = (a + b) / 2 × h — your numbers substituted and a diagram drawn. The perimeter is calculated too. Units can be mixed, and the answer comes in the units you need, hectares and acres included.

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01Calculator02Formula03Example04Mistakes05Nearby06Related
01

Calculator

enter the sizes — the formula and diagram follow

Trapezoid

area · perimeter
a = 6 cmb = 4 cmh = 5 cmcd
diagram · not to scale
Result
Area
25cm²
= 0.0025 m²
Perimeter
—enter c and d
How it was calculated
S = (a + b) / 2 × h = (6 + 4) / 2 × 5 = 25 cm²
← Other shapes and the composite shape
02

Formula

and what each letter means
Area
S = (a + b) / 2 × h
Perimeter
P = a + b + c + d
Notation
a, b
bases — the parallel sides
h
height — the distance between the bases
c, d
legs (needed for the perimeter)
03

Worked example

with real numbers
Givena = 6 cm, b = 4 cm, h = 5 cm
Solution
S = (a + b) / 2 × h = (6 + 4) / 2 × 5 = 25 cm²
Answer: area — 25 cm².
04

Common mistakes

The formula takes the height, not a leg: on a slanted trapezoid they differ.

First the half-sum of the bases, then multiply by the height — mind the brackets.

05

Nearby shapes

TriangleS = ½ × a × hParallelogramS = a × hRectangleS = a × bCalculatorAll 19 shapes, the composite shape and hectares →
м · км

Length converter

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%

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2·8·16

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