Three equal sides, three 60° angles, perfect symmetry — the equilateral triangle is geometry's favorite overachiever, and because every side is identical, you only need one measurement to unlock everything: the Side Length. Its area formula, A = (√3/4) × side², looks odd until you see where it comes from: drop a height from one vertex and the Pythagorean theorem gives height = (√3/2) × side, then the familiar half-base-times-height finishes the job. A side length of 6 gives an area of 9√3, about 15.59. Architects love equilateral triangles for trusses and geodesic domes because the symmetry distributes loads evenly; quilters and tilers love them because they tessellate into hexagons. Enter the side length and read the Area result. The tempting error is using the side length as the height in the base-times-height formula — the height is always shorter than the side, so if your answer seems too big, that shortcut is the likely culprit.

With the pre-filled defaults — Side Length 6 — the Area Of Equilateral Triangle Calculator returns Area 15.5885. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.