Parallelogram Calculator

A parallelogram has two pairs of equal, parallel sides, and this calculator needs just three measurements to describe one: the base, the height (the perpendicular distance between the base and its opposite side, not the length of the slanted side), and the side length itself. Area depends only on base and height — multiplying the two together — while the side length plays no role in the area calculation whatsoever; it exists purely to compute the perimeter, which needs the length of every side, base and slanted side alike. Because area never references it, changing the side field, no matter how much, leaves the reported area completely unchanged; only the perimeter reacts to it.

If you clear the side field so it evaluates to zero, the calculator quietly assumes the parallelogram is actually a rhombus and reuses the base length as the side length, rather than treating the field as missing. Growing the base while height stays fixed grows the area proportionally, the same way growing the height while base stays fixed would. Where this calculator falls short: it never checks whether the three numbers you enter can actually form a real parallelogram — geometrically, the height can never exceed the side length, since height equals the side length times the sine of the interior angle, which never exceeds one, but entering a height larger than the side still produces an area and perimeter, describing a shape that cannot exist.