Step 1: Measure the height, length, and width of the stairs in feet.

Step 2: Input a waste factor (as a percentage) and optionally the price per square foot.

Step 3: Calculate the total area and cost using the formula:

Formula: $$\text{Total Area} = (\text{Length} + \text{Height}) \times \text{Width} \times (1 + \text{Waste Factor})$$

Formula: $$\text{Total Cost} = \text{Total Area} \times \text{Price per Square Foot}$$

Let's say you have stairs with a height of 10 ft, length of 15 ft, width of 3 ft, a waste factor of 5% (0.05), and a price per square foot of $4.

Step 1: Calculate the total area:

$$\text{Total Area} = (15 + 10) \times 3 \times (1 + 0.05) = 25 \times 3 \times 1.05 = 78.75 \text{ sq ft}$$

Step 2: Calculate the total cost:

$$\text{Total Cost} = 78.75 \times 4 = 315$$

So, the total cost is $315.