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It's easy to assume that you'd calculate the volume of a triangular prism the same way you would for a pyramid . However, a triangular prism is a three-sided polyhedron with two parallel triangular bases and three rectangular faces. To calculate the volume, all you have to do is find the area of one of the triangular bases and multiply it by the height of the prism.

Part 1
Part 1 of 2:

Finding the Area of the Triangle

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  1. Look at the triangle and write down the base width and height. For example, your triangle might have a base of 8 cm and a height of 9 cm. [1]
    • Keep in mind that you're identifying the height of the triangle , not the entire prism.
    • You can use either of the triangular bases, since they should have the same dimensions.
  2. Once you know the width and height of the triangle, put the numbers into the formula for calculating triangular area: [2]
    • Area = 1/2 x width x height. You might also see it written as
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  3. In order to find the area of the triangular base for the prism, multiply the width by the height by 1/2. Remember to put the answer in square units because you're calculating area. [3]
    • For example, if the base is 8 and the height is 9, your formula will look like . The area of the triangle is 36 cm 2 .
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Part 2
Part 2 of 2:

Figuring the Volume of the Prism

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  1. Plug the triangular area into the formula to find the volume of the prism . The area of the triangle is 1 of the 2 numbers you need in order to find the prism's volume. In the formula , the triangular area is . [4]
    • To use the earlier example, the formula would be .
  2. Now you need to find the height of the triangular prism, which is the length of 1 of its sides. For example, the prism may be 16 cm high. Place this number in the place of the formula. [5]
    • For example, your formula should now look like .
  3. Since you now have all the parts of the equation, multiply the area by the height. The result will be the volume of the triangular prism. [6]
    • So, if , the answer is 576 cm 3 .
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Community Q&A

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  • Question
    How do I calculate the area of a triangular prism?
    Community Answer
    To find the surface area of a triangular prism, you would find the area of all the faces, then add them together.
  • Question
    How can I find the volume of a rectangular prism?
    Community Answer
    To find the volume of a rectangular prism, multiply the prism's width, height, and length. V = w*h*l
  • Question
    How do I find the volume of a square pyramid?
    Donagan
    Top Answerer
    V = (1/3)(s²)(h), where s is the length of a side of the base, and h is the height.
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      Tips

      • Ensure that the units of measurement are the same for all parts of the triangular prism before you begin the calculation. For example, if 1 part of the prism is in millimeters and the rest is in centimeters, convert the millimeters to centimeters first.
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      About This Article

      Article Summary X

      To calculate the volume of a triangular prism, first you need to find the area of one of the triangular bases by multiplying ½ by the base of the triangle and by the height of the triangle. For example, if the base is 8 and the height is 9, you would get ½ x 8 x 9 = 36. Therefore, the area is 36. Next, plug the area into the formula for finding the volume of a triangular prism, which is V = b x h, or volume equals the area of the base multiplied by the height of the prism. Now, plug the height of the prism into the formula and solve. As an example, if the area of the triangular base is 36 and the height of the prism is 16, you would get 36 x 16 = 576. Therefore, the volume of the triangular prism is 576. Write your answer in cubic units. If you want to learn how to calculate the height of a regular triangle, keep reading!

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