Whether you're planning on carpeting your stairs or simply replacing the hardwood, one of the facts you'll need to know is the total square footage of the stairs. While it seems like a daunting task, it's a surprising simple set of calculations that require a bit of measuring and some easy mathematics.
Measure the length and width of the horizontal surface of the second step from the bottom. In nearly all cases, this step will be approximately the same size as the other stairs and you can use these dimensions as your base number.
Multiply the two numbers to get the total number of square inches of the step. Measure the vertical surface of the same step, add the numbers and you'll have the average number of square inches for each step.
Count the number of steps and multiply that number times the average square inches of each step. If any of the steps are noticeably different when compared to the other steps, those steps should be measured separately and those numbers added to the total for the steps.
Measure any square or rectangular landing surface that may be included in the flight of stairs. Measure the width and length and multiply the numbers to calculate the square inches of the landing. Add that number to the total for the steps.
Multiply the total number of inches by 0.00694444444 to get the total square footage of the steps. Add at least 5 percent to the total to account for waste or mistaken cuts. That total number of square feet is how much material you will need.