If you’re ordering your own roofing materials, you’ll need to know exactly how big your roof is. This is typically done by measuring your roof’s square footage and its slope, which is a simple task. Here, our roofing experts explain how to measure a roof using both methods:

Square Footage

1. The first thing you’ll need to measure is the square footage of your roof.
2. Position your ladder at the corner of one of your roof planes to determine the length.
3. Extend your measuring tape as far as you can along the length of your roof and mark the area.
4. Move your ladder down to the next section. Beginning with where you marked the first measurement, measure the next section.
5. Continue measuring the length of your roof until you’ve covered the entire length area.
6. Write down the final measurement.
7. Next, you’ll want to measure the width of your roof plane. (Depending on how high your roof is, you may want to be up on it to take this measurement.)
8. Use your ladder or your feet to measure the entire width of your roof plane.
9. Write down the final measurement.
10. Continue steps 1-9 on each of your roof’s planes.
11. Multiply the length and width of each plane to get the square footage. Then, add all of your square footage measurements together to get the total square footage of your roof.

Slope

1. You’ll also need to measure the slope, or angle, of your roof.
2. To do this, position your ladder near the top point of your roof.
3. With your measuring tape, measure vertically from the top point to the bottom point of your roof. (This is also called the rise.)
4. Repeat this over 12 inches, then place the measurement over “12”. (For example: If your rise is 4 inches over 12 inches, then your slope measurement is 4/12.)