Equilateral Triangle Calculator
Calculate the area, perimeter, and height of an equilateral triangle from its side length.
This free online equilateral triangle 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.
Minimum: 0
All three sides are equal
Results
Area
43.3013 sq units
Perimeter
30 units
Height
8.6603 units
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Equilateral Triangle 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 Equilateral Triangle 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.
When to Use This Calculator
- •Use the Equilateral Triangle 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.
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Regular Polygon Area Calculator
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About Equilateral Triangle Calculator
An equilateral triangle is a triangle in which all three sides are equal and all three angles are 60 degrees. It is the most symmetric triangle and has numerous special properties. The area of an equilateral triangle is A = (√3/4)s², and its height is h = (√3/2)s. Equilateral triangles appear throughout mathematics, science, and design — from traffic signs and truss structures to molecular geometry (such as the arrangement of atoms in BF₃) and the faces of regular polyhedra. The equilateral triangle is one of only three regular polygons that can tile the plane by themselves (along with squares and hexagons). Six equilateral triangles form a regular hexagon. This calculator provides the area, perimeter, and height for any side length.
The Math Behind It
Formula Reference
Equilateral Triangle Area
A = (√3/4) × s²
Variables: s = side length
Height
h = (√3/2) × s
Variables: s = side length
Worked Examples
Example 1: Musical triangle
A musical triangle instrument has 20 cm sides.
Area ≈ 173.21 cm², Height ≈ 17.32 cm
Common Mistakes & Tips
- !Using ½ × base × side instead of ½ × base × height — the side is not the height.
- !Forgetting that the height of an equilateral triangle is not equal to the side length.
- !Confusing the area coefficient √3/4 with √3/2 (which is the height coefficient).
Related Concepts
Used in These Calculators
Calculators that build on or apply the concepts from this page:
Frequently Asked Questions
Are all equilateral triangles similar?
Yes. Since all angles are 60°, every equilateral triangle is similar to every other equilateral triangle, differing only in scale.
What is the ratio of height to side?
h/s = √3/2 ≈ 0.866. The height is about 86.6% of the side length.
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