Main perimeter
Enter your data and hit Calculate
Trapezoid perimeter calculator
Compute trapezoid perimeter by adding its 4 sides. Includes basic validation, units and decimals.
Trapezoid perimeter
Calculate the perimeter with four sides, isosceles or right mode.
Get the main perimeter plus conversions to mm, cm, m, inches and feet. Perfect for homework, classroom problems or quick design checks.
Inputs
e.g. 12.4
Bottom side.
e.g. 8.1
Top side.
e.g. 5.6
Oblique side 1.
e.g. 5.1
Oblique side 2.
e.g. 10
Bottom side.
e.g. 6
Top side.
e.g. 4.5
Both oblique sides are equal.
e.g. 9
Bottom side.
e.g. 5.5
Top side.
e.g. 3.2
Matches the perpendicular leg.
The main perimeter is displayed in the chosen unit.
0–10
Rounding applied to every output.
Results
Long base (B)
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Short base (b)
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Side c
—
Side d
—
Formula
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Perimeter conversions
mm
—
cm
—
m
—
in
—
ft
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How to find a trapezoid perimeter
The perimeter is simply every side added together. In the general case, you sum the long base, the short base and the two slanted sides. For an isosceles trapezoid, both slanted sides are equal, so you add the two bases and twice that leg. In a right trapezoid, one leg matches the height and the other is found with Pythagoras: subtract the bases, square that difference, add the square of the height, take the square root and add it to the remaining lengths.
The calculator normalizes every value to meters internally to avoid rounding issues, then shows the perimeter in your preferred unit plus equivalents in mm, cm, inches and feet.
Quick example
If an isosceles trapezoid has B = 12 cm, b = 7 cm and legs of 5 cm, the perimeter is the direct sum: 12 + 7 + 5 + 5 = 29 cm. The tool also displays the result in meters (0.29 m), millimeters (290 mm), inches and feet instantly.
What inputs do I need?
Use four side lengths in general mode. In isosceles mode, provide both bases and one leg. In right mode, enter the two bases and the height; the tool derives the slanted side automatically.
Can I mix units?
No. Enter all values in the same unit and select it in the dropdown. The calculator will handle all conversions for you.
