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# Calculators :: Plane Geometry :: Equilateral Triangle Calculator

Enter side, perimeter, area or altitude of equilateral triangle then choose a missing value and the calculator will show you a step by step explanation how to find that value.

## Equilateral Triangle Calculator

Input value you know and the value you want to find. You can enter either integers (10), decimal numbers(10.12) or FRACTIONS(10/3).

0 1 2 3 4 5 6 7 8 9 / . del
 Enter known values: side a = area A = perimeter P = altitude h =
 Select value to find: side a area A perimeter P altitude h
Show me an explanation.

# Formulas for Equilateral Triangle

To calculate missing value in equilateral triangle, based on one known value, you need to remember just three formulas.

 F1: $$P = 3 \cdot a$$ a = side h = altitude A = area P = perimeter F2: $$A = \frac{a^2 \sqrt{3}}{4}$$ F3: $$h = \frac{a \sqrt{3}}{2}$$

The diagram at the right shows when to use each of these formulas.

## Example 1:

If you are given altitude h and you want to calculate side a, then you need to use formula which connects h and a.

## Example 2:

If you are given area A and you want to calculate perimeter P then you need to make two steps to get the solution. In first step you apply formula which connects area A and side a and in second step use formula which connects side a and perimeter P.

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