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Equilateral triangle calculator

Compute the area, height and perimeter of an equilateral triangle from its side.

Related tools

All Geometry tools →
Triangle area calculator (Heron's formula)Compute a triangle's area from the length of its three sides.Triangle area calculatorArea of a triangle from base and height, three sides, or two sides and the angle between them.Angle Bisector Calculator (triangle)Enter the three sides or the three vertices and get the length of each internal angle bisector, the incenter, the inradius, and the exact point where every bisector cuts the opposite side. The angle bisector theorem is the heart of it: the bisector splits the opposite side in the ratio of the two adjacent sides. The triangle inequality is checked before anything is computed, and the triangle is drawn with its three bisectors.General Triangle SolverSolve any triangle from 3 known values (SSS, SAS, ASA/AAS, SSA) with the laws of sines and cosines: all sides and angles, area, perimeter and type, handling the ambiguous SSA case (0, 1 or 2 triangles).Sierpinski triangle generatorGenerate the Sierpinski triangle two ways: by recursive subdivision, which removes the central triangle at every level, or by the chaos game, where thousands of random midpoint jumps make the fractal emerge from pure randomness. Choose the depth or iteration count and a colour palette.Triangle Centroid CalculatorFind the centroid of a triangle from its three vertices, with the medians, side midpoints, median lengths and the 2:1 ratio, plus a diagram.Triangle Orthocenter CalculatorFind the orthocenter of a triangle (the intersection of its altitudes) from the three vertices, with the altitude equations and a diagram — note it can lie outside an obtuse triangle.Area calculatorCompute the area of a rectangle, square, circle or triangle.

The Equilateral triangle calculator turns Side length into Area, Height, Perimeter, instantly and for free. For instance, with Side length = 6 it returns Area = 15.589, Height = 5.196 and Perimeter = 18.

How to use it

  1. Enter your values: Side length.
  2. Read the result instantly: Area, Height, Perimeter.

Frequently asked questions

What does the Equilateral triangle calculator actually compute?

It takes Side length and derives Area, Height and Perimeter from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

A single value: Side length. Nothing else is required — no account, no file upload.

Can you show a worked example?

With Side length = 6, the calculator returns Area = 15.589, Height = 5.196 and Perimeter = 18. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Side length = 12 instead, Area goes from 15.589 to 62.354 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Side length = 3, Area comes out at 3.897. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Homework and site work alike: how much paint a wall takes, how much water a tank holds, whether a corner is square — and, on the coordinate side, the slope between two points, the distance across a plan, the midpoint of a span.

What is the most common mistake?

Mixing units inside one shape. Entering a length in centimetres and a width in metres gives an area wrong by a factor of a hundred, and the result looks perfectly plausible.

What is the difference between the Equilateral triangle calculator and the Triangle area calculator (Heron's formula)?

Both return Area and Perimeter. What differs is what they ask for: this one wants Side length, the Triangle area calculator (Heron's formula) wants Side a and Side b. Use whichever matches the numbers you already have.

Is there a tool for the next step?

Triangle area calculator is the closest one after this: Area of a triangle from base and height, three sides, or two sides and the angle between them.

What else is worth having open alongside it?

Angle Bisector Calculator (triangle) and General Triangle Solver — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
How-toHow to Find the Area of a Triangle: Base × Height and Heron's FormulaTwo reliable ways to find a triangle's area: half base times height when you know the height, and Heron's formula when you only know the three sides.ExplainerThe Pythagorean Theorem ExplainedIn a right triangle, a² + b² = c². Here's what the formula means, a worked example, how to find any side, and where it's used in real life.How-toHow to Calculate VolumeVolume is the space inside a shape. Here's how to find it for boxes, cylinders and spheres, and why keeping your units consistent is the whole game.How-toHow to Calculate the Square Metres of a RoomFind a room's area by multiplying length by width. Here's the method for rectangular, L-shaped and round rooms, and why area drives your material orders.How-toCircle: Circumference and AreaCircumference is 2πr, area is πr². Here's how radius, diameter and π fit together, both formulas worked through, and how not to mix them up.How-toHow Many Tiles Do You Need? (Floor and Wall)Estimate tiles from the area to cover and one tile's size, then add for cuts and waste. Here's the method, with an example and the 10% rule.
Equilateral triangle calculator — OneKitly