Step 3: Calculate
Now that you have your measurements, it’s time to calculate the square footage for each rectangle. Then you can add or subtract the square footages to find your total square footage for your area. Below is the measurement chart we created in Step 2. For each rectangle, multiply the length and width together. Divide the result by 144 and you have the square footage for that rectangle. We’ve recorded our numbers on the chart below.
After you have all the square footages of your rectangles, add them together. Be sure to skip any rectangles with square footage which is not ready to be added. In our example, rectangles F, H, and J cannot yet be included in the total. H and J must be halved before adding them, and F needs to be subtracted from the total. As shown below, adding up the square footages of the other rectangles gives us a current total of 410.5 square feet.
| Rectangle’s Letter | Length (inches) | Width (inches) | Rectangle’s Square Footage | Shortcut Notes |
| A | 40 | 24 | 6.6 | |
| B | 24 | 40 | 6.6 | |
| C | 24 | 36 | 6 | |
| D | 128 | 128 | 113.7 | |
| E | 24 | 46 | 7.6 | |
| F | 24 | 48 | (8 skip) | subtract from total |
| G | 216 | 156 | 234 | |
| H | 36 | 36 | (9 skip) | divide in half |
| I | 144 | 36 | 36 | |
| J | 36 | 36 | (9 skip) | divide in half |
| Total | 410.5 |
Dealing with skipped rectangles
Rectangle F: The square footage of rectangle F is 8. When we subtract 8 from 410.5 we get a new current total of 402.5 square feet.
Rectangles H and J: Half of H is 4.5 and half of J is 4.5 for a total of 9 feet to be added to our current total. 402.5 + 9 = 411.5 square feet.
Now that we know the actual square footage of our area, 411.5 square feet, our example owner is ready to shop for flooring materials. Depending on the flooring chosen, the owner may or may not need to add extra square footage to the order.