As a civil engineer, you might find yourself planning a roofing project, whether it’s for a client or your own home. One common question that arises is, “How many sheets of plywood do I need for a 1200 square foot roof?”

In this blog, we’ll break it down in a straightforward manner, provide practical examples, and help you grasp the essentials of calculating plywood requirements for your roofing project.


Before we get into the calculations, let’s establish some basic facts. Plywood is a standard choice for roof decking or sheathing. It provides a stable base for your roofing materials, such as shingles or tiles. The key is to determine how many sheets of plywood you’ll require to cover a 1200-square-foot roof effectively.

Calculating Plywood Requirements

To find out how many sheets of plywood you need, follow these simple steps:

Step 1: Measure the Roof

Measure the length and width of your roof in feet. For example, let’s say your roof measures 30 feet in width and 40 feet in length.

Step 2: Calculate the Area

Multiply the length by the width to find the total square footage. In this case, 30 feet x 40 feet equals 1200 square feet.

Step 3: Account for Plywood Size

Plywood sheets come in various dimensions, but the most common size is 4 feet by 8 feet. This means each sheet covers 32 square feet (4 feet x 8 feet).

Step 4: Divide and Round Up

Divide the total square footage of your roof by the coverage of one plywood sheet. In our example, 1200 square feet divided by 32 square feet per sheet equals 37.5 sheets. Since you can’t buy half a sheet of plywood, you’ll need to round up to the nearest whole number. So, you’ll need 38 sheets of plywood to cover the 1200 square foot roof.


When it comes to determining how many sheets of plywood you need for a 1200 square foot roof, it’s all about basic math. Measure your roof, calculate the area, consider the size of standard plywood sheets, and round up to ensure you have enough material to cover your entire roof adequately.


As a civil engineer and roofer, I love to share the experience that I have gained through the last couple of years. In the roofing industry, practical experience is a very crucial fact that can help you a lot. Hence, I want to help you with my blog.

Write A Comment