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Trapezoid Calculator
Last updated: June 19, 2026
A trapezoid calculator is a geometric tool that computes the area, perimeter, side lengths, and angles of a trapezoid. By entering the lengths of the two parallel bases and the height, the calculator determines the area using the formula where area equals the average of the bases multiplied by the height. It can also solve for missing angles or side lengths if coordinate points or side inputs are provided. Students and draftspersons use this tool to solve geometry homework and estimate land plots.
Enter the two parallel bases and the height to get the area. Add the two non-parallel sides for the perimeter.
Quick Answer
Calculate the area and dimensions of a trapezoid. Enter the bases and height to find the area and perimeter with formulas.
One of the two parallel sides. · e.g. 8
The other parallel side. · e.g. 12
Perpendicular distance between the bases. · e.g. 5
For perimeter. · e.g. 6
For perimeter. · e.g. 7
Area uses the two bases and the height. Add both non-parallel sides to also see the perimeter.
Area
50
((8 + 12) ÷ 2) × 5
Area = ((base 1 + base 2) ÷ 2) × height. Perimeter sums all four sides when both non-parallel sides are entered.
Examples
Bases 8 & 12, height 5
area 50
Bases 10 & 14, height 6, sides 7 & 7
area 72 · perimeter 38
Bases 3 & 9, height 4
area 24
How it works
A trapezoid has one pair of parallel sides (bases) and a height perpendicular to them. Area uses the average of the two bases, multiplied by the height. Perimeter sums all four sides directly.
Area · A = ((base 1 + base 2) ÷ 2) × height
Perimeter · P = base 1 + base 2 + side 1 + side 2
Height is perpendicular to the bases, not the slant side.
Related geometry calculators
- Area calculator for area across multiple 2D shapes.
- Perimeter calculator for perimeter and circumference in one place.
- Parallelogram calculator for the related shape with two pairs of parallel sides.
- Triangle area calculator with base & height, Heron, and SAS methods.
- All education calculators.
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Frequently asked questions
A trapezoid (called a trapezium in British English) is a four-sided polygon with exactly one pair of parallel sides. The parallel sides are called bases; the non-parallel sides are called legs. The height is the perpendicular distance between the two bases.
Take the average of the two parallel bases and multiply by the height: A = ((base 1 + base 2) ÷ 2) × height. For bases 8 and 12 with height 5, the area is ((8 + 12) ÷ 2) × 5 = 10 × 5 = 50 square units.
Add all four sides: P = base 1 + base 2 + side 1 + side 2. The two non-parallel sides (legs) are not equal to the height; the height is perpendicular to the bases while the legs slant. Enter both side lengths to get the perimeter.
An isosceles trapezoid has two equal non-parallel sides. The formulas are the same: enter the same value for both sides and the calculator returns the symmetric result. The same area formula works because it depends only on the bases and height.
A trapezoid is like a rectangle with one base that varies linearly from base 1 to base 2. Averaging the two bases gives the effective width of an equivalent rectangle with the same area, and multiplying by the height completes the area.
Technically a parallelogram has two pairs of parallel sides, so if you enter base 1 = base 2, the area reduces to base × height, which is the parallelogram formula. For a dedicated parallelogram calculator with its own input style, use the parallelogram calculator.
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