Blog

Triangle Area Calculator

Triangle area equals half the product of a base and its perpendicular height. The home tool uses that pattern when you pick Triangle in the shape list.

By Area Calculator

Open the calculator
Geometry shapes, grid paper, and measuring tools for area calculation guides

Quick Answer

A = ½ × b × h with h perpendicular to b.

Formula

  • A = ½ × b × h
  • Right triangle: legs can serve as b and h

Introduction

Area Calculator asks for base and height because that pair appears on most standardized diagrams and roof sketches.

Slant height along a slope is a common mistake. Height must meet the base at a right angle unless the problem defines another altitude.

Right triangles often use the two legs as base and height, which speeds up homework checks.

Main Content

What is it?

A triangle area calculator applies the half-base-times-height relationship to flat triangular regions.

Isosceles and scalene triangles still use the same rule once you identify the correct altitude for your chosen base.

Compare several numeric stories in area examples when you teach why halving the rectangle formula makes sense.

Formula

  • A = ½ × b × h
  • Heron's formula on paper when only three sides are known

Heron's formula uses three side lengths and half the perimeter. It is useful on tests but is not the input style on the home triangle mode.

Refresh the symbol meaning in the area formula guide if students confuse base with hypotenuse on right triangles.

Step-by-step guide

  1. Mark the base on your sketch Use the edge the problem names as base when possible.
  2. Draw or locate the altitude The height line must meet the base at 90°.
  3. Multiply then divide by two Half of base times height is the same as base times height divided by two.
  4. Verify in the tool Enter the same pair on Area Calculator and match your paper result.

Example

Base 10 m, height 4 m → 20 m².

Right triangle legs 6 and 8 → 24 square units.

Roof face: base along eave 12 ft, altitude 5 ft → 30 ft² per face before pitch adjustments your scope may add separately.

FAQ

Can I use the slant edge as height?
Only if the problem defines that segment as the altitude to your chosen base, which is rare on intro diagrams.
What if I only know three sides?
Use Heron's formula manually, or find the height with geometry tools appropriate to your course level.
Do units still square?
Yes. Meters times meters gives m², just like rectangles.

Conclusion

Triangle area is half of the rectangle you would get with the same base and height.

Train your eye to find the altitude before you multiply.

Open Area Calculator