How to Find the Height of a Triangle. Two Methods: Using Base and Area Equilateral Triangle. To calculate the area of a triangle you need to know its height. If this information is not given to you, you can easily calculate it based on what you do know!This article will teach you two different ways to find the height of a triangle, depending on what information you have been given.Ad.ow to Find the Height of a Triangle. Two Methods: Using Base and Area Equilateral Triangle. To calculate the area of a triangle you need to know its height. If this information is not given to you, you can easily calculate it based on what you do know!