How to Calculate the Area of a Sloped Surface

Hunker may earn compensation through affiliate links in this story.

Things You'll Need

  • Measuring tape

  • Calculator


With rectangular sloped objects you can simply measure the length and width with measuring tape, then multiply them to get the area.

At first glance, calculating the area of a triangular, sloped surface seems like an extremely tricky task. The average person knows that area is usually calculated by multiplying the length of an object by its width, but for a sloped surface one of those measurements is difficult to determine exactly, even with the help of a ruler or measuring tape. In reality, the Pythagorean theorem can be employed to accurately and quickly calculate the missing length or width measurement. The math involved is very simple and easily computed with a calculator.

Step 1

Measure the length of the sloped side of the surface as well as the other available side. Depending on the way the object is shaped, the missing side will either be the length or the width.

Step 2

Square both the sloped side and the other side measured (either the length or the width). These numbers will be plugged into the Pythagorean theorem to determine the length of the missing side.

Step 3

Subtract the squared number of the width (or length) side from the squared number of the sloped side.

Step 4

Take the square root of the number, and you have determined the measured side. Now that you have both the length and width, multiply them to obtain the area of the sloped surface.


James Wiley

James Wiley graduated from Providence College in 2009 as a double major in global studies and Spanish. Wiley's capstone thesis paper was published in the Providence College database. He has also competed in international script-writing competitions and coauthored a pilot which placed in the top 15 percent of international entries over the past year.