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Trapezoid Calculator: Area, Median and Perimeter

This free trapezoid calculator finds the area and the median of a trapezoid from its two parallel sides and its height. Add the slanted sides to get the perimeter as well.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

A trapezoid has one pair of parallel sides. Roof ends, ramps, cross-sections of channels and many bags are trapezoids.

Enter the parallel sides and the height.

How to Use This Tool

  1. Enter the value or values asked for in the boxes.
  2. Choose the unit label if there is a choice.
  3. Press Calculate.
  4. Read every result in the table and copy what you need.

How the Calculation Works

Area = ½(a + b)h. Median = (a + b) ÷ 2. Perimeter = a + b + c + d when the slanted sides are given. For an isosceles trapezoid with equal legs, the leg is √(h² + ((b − a) ÷ 2)²).

Worked Example

With parallel sides 4 and 6 and height 3, the area is 15 and the median 5. With slanted sides of 3.162 each, the perimeter is 16.32.

Common Uses

  • Roof and gable shapes.
  • Channels and ramps.
  • Land plots.
  • Homework.

Tips and Common Mistakes

  • The height is the straight distance, not a slanted side.
  • Leave the slanted sides empty if you only need area.
  • Use one unit throughout.
  • Measure carefully: a small error in a length is squared in an area and cubed in a volume, so a 5 percent error in a side can become a 10 percent error in the area or a 15 percent error in the volume.
  • Round only at the end. If you copy a result into another calculation, copy the full number from the tool rather than a rounded one, so small errors do not build up.

Next, you may need the rhombus calculator, rectangle calculator, regular polygon calculator, ellipse calculator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

Area = ½ × (a + b) × h, the average of the two parallel sides times the height.
The line halfway between the parallel sides. Its length is (a + b) ÷ 2.
Add all four sides. You need the two slanted sides for that.
In British English, a trapezium is what Americans call a trapezoid.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.