Quadrilateral Calculator

How to use

1. 1Pick a shape: Rectangle, Parallelogram, Trapezoid, Rhombus, or Kite. The input fields and diagram update to match.
2. 2Choose the length unit (mm, cm, m, km, in, ft, or yd). Area uses the same unit squared. The tool does not convert between units.
3. 3Fill in the inputs. Rectangle needs length and width. Parallelogram needs base, slant side, and perpendicular height. Trapezoid needs both bases and the height; leg lengths are optional and an isosceles trapezoid is assumed if you leave them empty. Rhombus offers three modes: both diagonals, side plus one diagonal, or side plus an interior angle. Kite needs both pair sides and both diagonals.
4. 4Read the results panel for area, perimeter, diagonals, and shape-specific extras. Each row has a small Copy button.
5. 5Click Copy summary to capture every input and result in a single block ready to paste into a worksheet, a quote, or a note.
6. 6Use Clear inputs to reset the fields for the current shape so you can model a different example.

About this tool

Quadrilateral Calculator solves the five quadrilaterals you actually use outside of a competition math class: rectangle, parallelogram, trapezoid, rhombus, and kite. Pick a shape, enter the values printed on the diagram (length and width for a rectangle, base and slant side and perpendicular height for a parallelogram, two bases and a height for a trapezoid, two diagonals or a side plus an angle for a rhombus, two pair sides plus both diagonals for a kite) and the calculator returns area, perimeter, and the diagonal lengths along with shape-specific extras: rectangle diagonal by the Pythagorean theorem, parallelogram acute and obtuse interior angles plus the long and short diagonals from the law of cosines, trapezoid midsegment and inferred legs for the isosceles case, rhombus side and height and acute and obtuse angles from any of three input combinations, and a closure check on the kite that catches inconsistent diagonals before they hide a wrong answer. A switchable length unit applies the same label to every length output and uses the squared form for area, so you can work in millimeters, centimeters, meters, kilometers, inches, feet, or yards without converting. Diagrams show the labels next to the standard textbook letters (b for base, s for side, h for height, p and q for diagonals, b1 and b2 for the bases of a trapezoid) so the inputs match the figures in a geometry book or a fabrication drawing. Everything runs locally in your browser; nothing you type is uploaded.

Free to use. Works in your browser. No signup, no login.