Stair Carpet Calculator

This stair carpet calculator will help you figure out the dimensions of the carpet you will need to cover flights of stairs. Knowing precisely how much carpet you'll need will help you decide how much to purchase and could save you from spending too much. In this carpet calculator, you will learn:

• The basics of installing carpets on stairs;
• How to use this stair carpet calculator; and
• How to calculate stair carpet yourself.

As an added feature, this tool also works as a stair carpet cost calculator.

Ready to start learning? Then keep on reading. 🙂

Carpeting stairs follows the same procedure as carpeting a large floor area. We use the same materials and tools like hammers and nails, staplers or tackers to affix our carpet to the surface, utility knives or hook blades to cut the carpet, and carpet knee kickers, power stretchers, or carpet tuckers to stretch and position our carpets.

The installation of stair carpets can start from the lower floor to the higher floor or landing, or vice versa. For stairs that have overhanging stair nosings, it is easier to install the carpet going up as it will be easier to tuck and staple the carpet underneath the stair nosings. On the other hand, you won't have any problems installing a carpet going down the staircase if the steps don't have overhanging nosings.

Like any flooring materials and wall claddings alike, we want to, as much as possible, have the least amount of scrap we can get after installing these materials. Other materials that we might need for the installation are tack strips, underlayment materials, and the optional double-sided adhesive tapes. In this calculator, our focus is on the amount of carpet we'll need. If you're installing other flooring materials, we have a separate flooring calculator that you can use for that.

Our stair carpet calculator is very intuitive and easy to use. Here are the steps you can follow to use this tool effectively:

1. Enter the details of your stair:
   • Number of steps - we consider every floor rise as one step;
   • Riser rise - the difference in elevation of or the vertical distance between two adjacent steps;
   • Effective tread run - horizontal distance between same points on two adjacent steps (e.g., riser to riser measurement);
   • Landing depth - if applicable, this measurement is the length of your stair landing along with the direction of the flight of stairs; and
   • Stair width - the distance between the two walls on both sides of the stairs or the stair tread length.

2. If your stair nosings have overhangs, answer yes to the With stair nosing overhang? question. Answer no if they don't have any.

3. If you selected yes in the second step, you would see that a Stair nosing details section will pop up within the tool. Here, you have to:

   a. Select the shape of your stair nosing; and

   b. Enter the measurements of the stair nosing's overhang and thickness.

4. Input the allowances you want for your carpet. You may want to have up to a foot of an allowance for the carpet length and an inch or two for the carpet width allowance. We set these allowances as part of a contingency plan if you ended up using an imprecise measuring tool or your stair has wide areas at some point of the flight.

After these steps, our calculator will display your required carpet length and width. At the same time, you will also see the carpet area if you want to estimate how much your carpet will cost. You can then click on the Cost details and results heading of our tool to use it as a stair carpet cost calculator.

Now that we know how to use our tool as a simple stair carpet calculator and a stair carpet cost calculator, how about we consider an example and learn how to calculate stair carpets manually? Let's do that in the next section of this text.

The best way to learn how to calculate stair carpet sizes is by trying to solve a problem. Let's say we first want to carpet the first portion of a staircase to look something like this:

In this portion of the staircase, we need to cover a 4-step flight of stairs that has measurements of 18.0 cm for its riser rise, 25.0 cm for its effective tread run, and a landing depth of 1.0 m (or 100 cm). The steps also have 2.0 cm-thick rounded bullnose stair nosings that overhang 2.5 cm beyond the risers. It is also good to note that this flight of stairs is 1.0 m wide.

Here is a closer look at the step and nosing details:

And in this illustration, you can see the landing depth and the stair width:

Now, let's start by determining the length of carpet that can cover the area highlighted with green color, as shown below:

As you can see, this will be the carpet section covering the riser and the nosing overhang. We can calculate the length of carpet to cover this area using this formula:

where:

• $V$ - Length of carpet to cover the riser and the overhang;
• $R$ - Riser rise;
• $t$ - Nosing thickness; and
• $P_\text{shape}$ - Exposed nosing perimeter.

Since we have a rounded (or bullnose) stair nosing, we can calculate $P_\text{shape}$ using this equation:

where:

• $P_\text{⭘}$ - $P_\text{shape}$ for rounded nosing;
• $o$ - Nosing overhang; and
• $t$ - Nosing thickness.

If in case the nosing has a rectangular shape or triangular, here are the equations we could use for those, respectively:

Since we have a rounded nosing, we can plug the $P_\text{⭘}$ expression into our first equation and substitute the variables with their corresponding measurements to determine $V$, as we can see here:

From our stair illustration, $V$ appears four times just like the number of steps there are on our flight of stairs. Consequently, there are three treads on our stairs, or a number less than the number of steps. We get the carpet length we need to cover this area by summing up these measurements. In equation form, we express that as:

where:

• $L$ - Carpet length for a flight of stairs;
• $n$ - Number of steps on this stairs;
• $R$ - Riser rise;
• $t$ - Nosing thickness, if applicable;
• $P$ - Exposed nosing perimeter; and
• $T$ - Effective tread run.

Again, substituting our known measurements gives us:

Finally, to complete the carpet length we need, we should add any carpet length we need to cover the landing of this flight of stairs. It could be the depth of a platform leading to another flight of stairs or an area before transitioning to another carpeted floor or another flooring material. Now is also the best time to consider adding an allowance for your carpet length. In equation form, we have:

where:

• $L_\text{total}$ - Total carpet length for a flight of stairs;
• $D$ - Landing depth; and
• $\text{allowance}$ - total allowance to cover any measurement errors or discrepancies.

Let's say we want to have an allowance of 10 cm; we now solve for the total carpet length as shown below:

For the width of our carpet, we can order a rug with the same width as our stair steps. However, to consider any deviations of the stair width throughout the staircase, perhaps due to errors in the stair's construction, it's also a good practice to consider adding an allowance to the width of the carpet. This allowance can also give you a choice to scrunch and tuck your carpet's edge against the wall or the stringers of your stairs.

Say we want a 1.0 cm allowance to both sides of our carpet for the purpose mentioned earlier, we then have to inform our supplier to provide us with a 102.0-cm wide carpet that is about 274 or 280 cm long for this flight of stairs.

Almost every supplier of do-it-yourself carpeting materials prices their rugs per unit area. That means it's better to know the area you need to cover with carpet if you want to calculate the cost of the stair carpet you need. So from our example earlier, we first need to calculate our needed carpet area as follows:

where:

• $\text{area}$ - Carpet area needed for a flight of stairs;
• $L_\text{total}$ - Total carpet length for this flight of stairs; and
• $W_\text{total}$ - Total carpet width for this flight of stairs.

Then, we multiply our calculated carpet area by the price of our carpet of choice. Let's say we got a great deal of $32 per square meter of high-quality carpet. We calculate our total carpet cost in this fashion: