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Trapezoid Area Calculator

Trapezoid Area Calculator is part of Toolspire and is ready as soon as this page loads. The height must be the perpendicular distance between the parallel sides, not the slanted leg. A leg that is longer than the height will overstate the area if you type it as height.

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What you can do here

Only the parallel pair

The slanted sides are not inputs. They do not appear in this formula.

Either order of the bases

3 and 5 is the same area as 5 and 3.

16 is the check

The average base is 4, times height 4, is 16.

The sequence

How to use the Trapezoid Area Calculator

  1. 1

    Measure the two parallel sides

    If no sides are parallel, this is not a trapezoid and Heron’s formula may be the triangle you actually have.

  2. 2

    Drop a perpendicular for the height

    Do not type the slanted edge.

  3. 3

    Confirm 16

    Bases 3 and 5, height 4.

Worth knowing

  • Trapezoid Area Calculator on Toolspire: area = (a + b) / 2 × height.
  • (3 + 5) / 2 × 4 = 16.
  • The height is perpendicular, between the two parallel sides.
  • Sides and height must be positive. A zero height is a line, and the area is refused rather than shown as zero.

Average the parallel sides, then multiply

A trapezoid’s area is the average of the two parallel sides times the perpendicular height between them. Averaging 3 and 5 gives 4, and 4 times a height of 4 is 16. Using a slanted side as the height makes the figure taller than it is. The non-parallel sides are needed only if you are finding the height yourself from other measurements.

FAQ

Questions about Trapezoid Area Calculator

Where does Trapezoid Area Calculator run?

Trapezoid Area Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What is the area for bases 3 and 5 and height 4?

16.

Does the order of the bases matter?

No. Addition is commutative.

What if I only know the slanted side?

You do not yet have the height. Find the perpendicular distance first. This page will not treat the leg as the height.

Is a parallelogram a special case?

Yes, when the parallel sides are equal. The formula then becomes base times height, which is correct for a parallelogram too.

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