Half of base times height — the first area formula most students memorize, and the one that quietly underlies half of geometry. Every triangle is half of some parallelogram, which is why the ½ is there: A = ½ × base × height. The height must be perpendicular to whichever side you call the base, and for an obtuse triangle that perpendicular may fall outside the triangle entirely, which confuses beginners but changes nothing about the formula. With Base = 6 and Height = 4, the area is 12. Roofers estimating gable ends, sailors computing sail area, and students grinding through homework all use this one line of math. Enter your base and height and read the Area result. The classic mistake is grabbing a slanted side as the height — always drop the perpendicular, even if you have to sketch it. And note the base is not special: any of the three sides can serve as the base, as long as the height matches it.

With the pre-filled defaults — Base 6, Height 4 — the Area Of Triangle Calculator returns Area 12.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.