Plane Shapes: Area & Perimeter Calculators

Area, perimeter and diagonal calculators for the standard 2D figures — triangles, quadrilaterals, ellipses and polygons. The most-searched geometry tools, used for homework, material takeoffs and layout work.

4 calculators in this category

Which one do you need?

Triangle Area Calculator
Find the area of any triangle from base and height, three sides using Heron's formula, or two sides and the included angle, with every step shown.
Rectangle Area & Perimeter Calculator
Solve rectangle area, perimeter, diagonal and aspect ratio from any two known values, including the awkward case where only area and perimeter are given.
Trapezoid Area & Perimeter Calculator
Compute trapezoid area, midsegment, perimeter and base angles from the parallel sides, height and legs, or back-solve the height from a known area.
Hexagon Area & Across-Flats Calculator
Find the area, side, across-flats and across-corners size of a regular hexagon from any one dimension. For hex bar stock, fasteners and hex tile.

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