Trapezoid Area Calculator
Calculate the area of a trapezoid.
About Trapezoid Area Calculator
Trapezoid area = ½(sum of parallel sides) × height. A rectangle is a special trapezoid where a = b.
$$A = \frac{1}{2}(a+b)h$$
How to use this calculator
- Enter the length of the first base.
- Enter the length of the second base.
- Enter the perpendicular height.
- Click calculate to get the area.
The formula explained
$$ A = \frac{(b_1 + b_2)}{2}h $$
- \(A\) = area of the trapezoid
- \(b_1\) = length of one base
- \(b_2\) = length of the other base
- \(h\) = height, the perpendicular distance between the bases
Step by step method
- Add the two base lengths together.
- Divide that sum by 2 to find the average base length.
- Multiply the result by the height.
- The product is the area of the trapezoid.
Worked example
For a trapezoid with bases 8 cm and 14 cm and height 6 cm, here is how to find the area.
- Add the bases: \(8 + 14 = 22\).
- Find the average base length: \(22 \div 2 = 11\).
- Multiply by the height: \(11 \times 6 = 66\).
Answer. 66 square centimeters
Tips and common mistakes
- Use the perpendicular height, not a slanted side length.
- Make sure all measurements use the same unit before calculating.
- If your bases are labeled top and bottom, either one can be \(b_1\) or \(b_2\).
- Remember that area is always written in square units.
Frequently asked questions
What measurements do I need?+
You need the lengths of both parallel sides and the perpendicular height between them. Those three values are enough to find the area.
Does it matter which base I enter first?+
No. The two bases are added together, so the order does not change the result. You can put either base in either field.
Can I use inches, centimeters, or feet?+
Yes, any unit works as long as you keep everything consistent. The final area will be in square units based on the unit you choose.
What if I only know the slanted side length?+
That is not enough on its own for the area. You need the perpendicular height, not a slanted edge, unless you can first find the true height.
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