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Trapezoid Area Calculator

A trapezoid has one pair of parallel sides. Enter those two sides and the perpendicular height between them to get the area and the median. Add the two slanted legs as well if you want the perimeter.

Quick examples

The perpendicular distance between the parallel sides.

Enter both slanted sides to get the perimeter.

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Area50 ft²
Median (midsegment)
10 ft
Perimeter
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      Formula

      Area = ½ × (a + b) × height
      Median (midsegment) = (a + b) ÷ 2
      Perimeter = a + b + c + d

      How to use it

      1. Enter the two parallel sides, a and b.
      2. Enter the height — the straight-line gap between them at a right angle.
      3. Optionally enter the two legs to get the perimeter.

      Worked examples

      Parallel sides of 8 ft and 12 ft, 5 ft apart: 50 ft², which is 4.645 m²

      Area
      50 ft²
      Median (midsegment)
      10 ft

      A right trapezoid: bases 6 m and 9 m, height 4 m, legs 4 m and 5 m

      Area
      30 m²
      Median (midsegment)
      7.5 m
      Perimeter
      24 m

      Why the formula works

      The median is the average of the two parallel sides, and a trapezoid has the same area as a rectangle that wide and just as tall. So with parallel sides of 8 and 12 and a height of 5, the area is 10 × 5 = 50.

      Trapezoid or trapezium

      In US English a trapezoid has exactly one pair of parallel sides. In British English the same shape is called a trapezium. The formula is identical.

      Questions people ask

      What is the area of a trapezoid with bases 8 and 12 and height 5?

      ½ × (8 + 12) × 5 = 50 square units.

      Can I use a slanted side as the height?

      No. The height must be perpendicular to the parallel sides. A slanted leg is longer than the height and would overstate the area.

      How do I find the height from the area?

      Rearrange the formula: height = 2 × area ÷ (a + b). An area of 50 with bases 8 and 12 gives a height of 5.

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