Geometry Calculators

Trapezoid Calculator

Calculate the area, perimeter and diagonals of a trapezoid from its side lengths and perpendicular height.

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Trapezoid Calculator

Enter the two parallel bases, the two non-parallel sides and the perpendicular height, then select Calculate.

Enter the length of the first parallel side.
Enter the length of the second parallel side.
Enter the length of the first non-parallel side.
Enter the length of the second non-parallel side.
Enter the perpendicular height between the bases.
All entered measurements must use the same unit.
Choose how many decimal places are displayed.
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What Is a Trapezoid Calculator?

A trapezoid calculator is a geometry tool used to calculate measurements of a trapezoid from known side lengths and height. A trapezoid is a four-sided polygon with at least one pair of parallel sides, known as the bases.

This free online calculator can be useful for students, teachers, engineers, designers, builders and anyone working with geometric measurements. Enter the two parallel bases, both non-parallel sides and the perpendicular height to calculate the trapezoid's area, perimeter and diagonals.

Why Use Trapezoid Calculator?

This calculator brings several common trapezoid calculations together in one simple interface, helping you obtain useful geometric measurements without performing each formula manually.

1

Calculate Area

Calculate the area of a trapezoid using its two parallel bases and perpendicular height.

2

Find Perimeter

Add all four side lengths to quickly determine the trapezoid's perimeter.

3

Calculate Diagonals

Calculate both diagonal lengths when the supplied measurements describe a valid trapezoid.

4

Multiple Units

Work with millimetres, centimetres, metres, inches, feet or yards.

5

Adjustable Precision

Choose two, four or six decimal places for the displayed results.

6

Instant Results

Perform the calculations directly in your browser without installing additional software.

How to Use the Trapezoid Calculator

Use the calculator by entering the required trapezoid measurements and selecting the appropriate unit and display precision.

  1. Enter the Top Base — Enter the length of one of the trapezoid's parallel sides.
  2. Enter the Other Measurements — Enter the second base, both non-parallel sides and the perpendicular height.
  3. Select Unit and Precision — Choose the length unit used for all measurements and the number of decimal places to display.
  4. Calculate and Review — Select Calculate to display the area, perimeter and diagonal lengths.

Trapezoid Calculator Formulas

The main formula for the area of a trapezoid uses the lengths of its two parallel bases and the perpendicular distance between them. If the bases are represented by a and b, and the height is h, the area is calculated as A = ½(a + b)h.

The perimeter is found by adding all four side lengths. If the two bases are a and b and the remaining sides are c and d, the perimeter is P = a + b + c + d. The diagonals depend on the relative positions of the sides, bases and height, so their calculation requires the complete set of measurements entered into the calculator.

How to Calculate the Area of a Trapezoid

To calculate trapezoid area, add the lengths of the two parallel bases, divide their sum by two, and multiply the result by the perpendicular height. For example, a trapezoid with bases of 8 cm and 12 cm and a height of 4 cm has an area of 40 cm²: ½ × (8 + 12) × 4 = 40 cm².

How to Calculate the Perimeter and Diagonals

Trapezoid perimeter is straightforward because it is the sum of all four sides. Diagonals are more dependent on the trapezoid's geometry. This calculator determines the horizontal offsets implied by the supplied side lengths and height and then uses the Pythagorean theorem to calculate the two diagonals.

Trapezoid Calculator Accuracy

All calculations are performed directly in your browser using JavaScript. Your measurements are not sent to a server by the calculator. The selected decimal-place setting controls how results are displayed and rounded; calculations themselves use the underlying numerical values.

For accurate results, make sure every measurement uses the same length unit and that the values describe a geometrically valid trapezoid. The height must be the perpendicular distance between the two parallel bases, rather than the length of either non-parallel side.

James William Steven Parker, creator of YesTools
Created by

James William Steven Parker

Creator & Developer of YesTools

James William Steven Parker is a web developer and technology professional with extensive experience in web development, web design, SEO, web hosting, systems analysis and cybersecurity. He created YesTools to provide fast, practical and free online tools for everyday tasks and technical work.

Learn more about James and YesTools

Frequently Asked Questions

A trapezoid is a four-sided polygon with at least one pair of parallel sides. The two parallel sides are commonly called the bases, while the other two sides are called the legs.
This trapezoid calculator calculates the area and perimeter of a trapezoid and, when the supplied measurements describe a valid trapezoid, calculates both diagonal lengths.
To calculate the area of a trapezoid, you need the lengths of its two parallel bases and its perpendicular height. This calculator also accepts both non-parallel side lengths so it can calculate the perimeter and diagonals.
The area of a trapezoid is calculated using A = ½(a + b)h, where a and b are the lengths of the two parallel bases and h is the perpendicular height between them.
The perimeter of a trapezoid is calculated by adding the lengths of all four sides: P = a + b + c + d.
Yes. A trapezoid can have equal non-parallel sides. This type of trapezoid is commonly called an isosceles trapezoid.

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