Triangle Area Calculator
Calculate the area of a triangle using base and height. The classic formula A = ½ × base × height.
This free online triangle area calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
The length of the base of the triangle
The perpendicular height from the base to the opposite vertex
Results
Area
30 sq units
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Triangle Area Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Triangle Area Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Triangle Area Calculator Formula
See calculator inputs for the governing equation
Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.
When to Use This Calculator
- •Use the Triangle Area Calculator when you need a quick mathematical result without writing out all the steps manually, saving time on repetitive calculations.
- •Use it to verify hand calculations on tests or assignments and catch arithmetic mistakes.
- •Use it when teaching or explaining mathematical concepts to others, demonstrating how changing inputs affects the result.
- •Use it to explore the behavior of mathematical functions across a range of inputs.
About This Calculator
The Triangle Area Calculator is a free mathematical calculation tool for students, educators, and professionals who need quick, reliable results. Calculate the area of a triangle using base and height. The classic formula A = ½ × base × height. The underlying algorithms implement well-established mathematical formulas and numerical methods. Results are computed instantly in the browser. This tool is useful for learning, verification of hand calculations, and rapid exploration of mathematical relationships. All computation happens locally — no data is sent to a server.
About Triangle Area Calculator
The triangle is one of the most fundamental shapes in geometry, and calculating its area is a skill used across mathematics, engineering, architecture, and science. A triangle is a polygon with three edges and three vertices. The simplest way to compute its area is with the formula A = ½ × base × height, where the height is the perpendicular distance from the chosen base to the opposite vertex. This formula works for all types of triangles — acute, right, and obtuse. Triangles are the building blocks of more complex polygons; any polygon can be divided into triangles, making triangle area a cornerstone concept. From surveying land parcels to designing roof trusses, this calculation appears constantly in practical applications. This calculator gives you the area instantly when you provide the base and height measurements.
The Math Behind It
Formula Reference
Triangle Area
A = ½ × b × h
Variables: b = base, h = perpendicular height
Worked Examples
Example 1: Sail area
A triangular sail has a base of 8 m and a height of 12 m.
A = 48 square meters
Example 2: Road sign
A yield sign has a base of 36 inches and height of 31.2 inches.
A = 561.6 square inches
Common Mistakes & Tips
- !Using a slant side instead of the perpendicular height.
- !Forgetting to multiply by ½, which gives the area of the full parallelogram instead.
- !Confusing the altitude (height) with one of the sides of the triangle.
Related Concepts
Used in These Calculators
Calculators that build on or apply the concepts from this page:
Frequently Asked Questions
What if I do not know the height?
Use Heron's formula if you know all three sides, or use A = ½ab sin(C) if you know two sides and the included angle.
Does the formula work for obtuse triangles?
Yes. The height may fall outside the triangle for obtuse triangles, but the formula A = ½bh still applies when the perpendicular height is measured correctly.