Trapezoid: Definition, Properties & Formulas

Trapezoid: Definition, Properties & Formulas
Coming up next: What is Surface Area? - Definition & Formulas

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:02 Definition of a Trapezoid
  • 0:26 Special Trapezoids
  • 1:28 Properties of a Trapezoid
  • 2:26 Practice
  • 3:30 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up


Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Jennifer Beddoe
A trapezoid has one pair of parallel sides. Learn more about the properties and formulas of trapezoids in this lesson. A quiz following the lesson will allow you to solidify what you've learned.

Definition of a Trapezoid

Image of a trapezoid

A trapezoid is a 2-dimensional geometric figure with four sides, at least one set of which are parallel. The parallel sides are called the bases, while the other sides are called the legs. The term 'trapezium,' from which we got our word trapezoid has been in use in the English language since the 1500s and is from the Latin meaning 'little table.'

Special Trapezoids

There are a few special trapezoids that are worth mentioning.

In an isosceles trapezoid, the legs have the same length and the base angles have the same measure.

Isosceles trapezoid

In a right trapezoid, two adjacent angles are right angles.

Right trapezoid

If the trapezoid has no sides of equal measure, it is called a scalene trapezoid.

Scalene trapezoid

A parallelogram is a trapezoid with two sets of parallel sides.


There is actually some controversy over whether a parallelogram is a trapezoid. One group states that the definition of a trapezoid is having only one set of parallel sides, which would exclude the parallelogram because it has two sets of parallel sides. The other, more mainstream group, states that the definition of a trapezoid is having at least one set of parallel sides, which includes the parallelogram. For our discussions, because it is the more widely accepted view, we will consider a parallelogram to be a trapezoid.

Properties of a Trapezoid

The formula for the perimeter of a trapezoid is P = (a + b + c + d). To find the perimeter of a trapezoid, just add the lengths of all four sides together.

The formula for the area of a trapezoid is A = (1/2)(h)(a + b), where:

  • h = height (This is the perpendicular height, not the length of the legs.)
  • a = the short base
  • b = the long base

Dimensions of a trapezoid

An isosceles trapezoid has special properties that do not apply to any of the other trapezoids:

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account