How Much Concrete Do I Need for Stairs?

How Much Concrete Do I Need for Stairs?

For a typical set of 4 concrete steps at 48 inches wide with an 11 inch run and 7 inch rise, plus a small top platform, you need roughly 24 cubic feet of concrete, or about 0.88 cubic yards. That is around forty 80 lb bags, or a bit under a yard of ready-mix. The exact number depends on your step count, width, and whether you fill or hollow out the form.

I have poured a lot of stairs, and what trips people up is that stairs are not a simple slab. They are a wedge. Here is how to size the pour so you do not end up short.

Why Stairs Are a Triangular Stack

Think of stairs as a stack of rectangular blocks, each shorter front-to-back than the one below it. From the side, the mass forms a triangle: the bottom step carries the full depth above it, while the top step is just one tread deep.

The volume of a single step block is:

width × run × rise

• width is how wide the stairs are, side to side
• run is the tread depth, how far your foot goes back on each step
• rise is the height of each step

Because they stack into a triangle, double the steps and you more than double the concrete. That is why an eyeball guess is usually wrong and why a concrete steps calculator saves you from ordering short.

The Formula in Plain Text

Here is the method I use every time. Convert every measurement to feet first (divide inches by 12):

1. For each step, the cross-section area it adds is: run × (step number × rise). Counting from the top, step 1 is 1 rise tall, step 2 is 2 rises tall, and so on down.
2. Add up all those cross-section areas.
3. Multiply the total by the width for cubic feet.
4. Add any top platform or landing.
5. Divide by 27 to get cubic yards.

If you want the background on that divide-by-27 step, see our guide on how to calculate concrete yards.

Worked Example: 4 Steps, 48 Inches Wide

Real numbers to follow:

• Width: 48 in = 4 ft
• Run (tread): 11 in = 0.917 ft
• Rise: 7 in = 0.583 ft
• Steps: 4
• Top platform: 12 in deep = 1 ft, one riser thick

Step cross-sections (run × step number × rise):

• Top step: 0.917 × 1 × 0.583 = 0.535 sq ft
• Second step: 0.917 × 2 × 0.583 = 1.069 sq ft
• Third step: 0.917 × 3 × 0.583 = 1.604 sq ft
• Bottom step: 0.917 × 4 × 0.583 = 2.139 sq ft

Add those up: 0.535 + 1.069 + 1.604 + 2.139 = 5.35 sq ft of cross-section. Multiply by the 4 ft width: 5.35 × 4 = 21.4 cubic feet for the steps.

Now the top platform: 4 ft wide × 1 ft deep × 0.583 ft thick = 2.33 cubic feet.

Total: 21.4 + 2.33 = 23.7 cubic feet. Divide by 27: 23.7 ÷ 27 = 0.88 cubic yards.

That is your order. Round up and add about 10 percent for waste and over-excavation, so I would get a full cubic yard or plan on the full 40 bags.

Quick Reference Table

These assume a standard 48 inch (4 ft) width, 11 inch run, 7 inch rise, and a small 12 inch top platform. The 80 lb bag figure uses 0.60 cubic feet per bag, rounded up.

Steps	Cubic Feet	Cubic Yards	80 lb Bags
3	15.2	0.56	26
4	23.7	0.88	40
5	34.4	1.28	58
6	47.3	1.75	79

Notice how fast it climbs: 3 steps to 6 is not double the concrete, it is triple.

Bags vs. Ready-Mix: When to Switch

My rule of thumb: under about 1 cubic yard, mixing 80 lb bags yourself is doable but sweaty. That 4-step example at 40 bags is right at the edge of what I would hand-mix. At 5 steps or more, order ready-mix. Fifty-plus bags is a full day of hauling, and stairs need to be poured in one continuous shot so they cure as a single monolithic piece.

Run your final number through the ready-mix calculator for the truck cost, or the concrete bag calculator if you are staying with bags. For the big picture, our how much concrete do I need guide covers it all.

Save Concrete With Hollow Forms

Here is a trick that cuts your order and cost: you do not have to pour solid stairs. Build the form, then fill the middle of the wedge with compacted gravel, rubble, or foam blocks before you pour. You only need a solid shell 5 to 6 inches thick over the fill.

On that 4-step example, filling the core can drop your concrete from nearly a yard to half a yard, and it lightens the load on the footing. Just compact the fill tight so it does not settle and crack the shell.

Rebar for Stairs

Stairs carry point loads and cantilever off the footing, so they need reinforcement. I run #4 (half inch) rebar horizontally along each tread and vertical dowels every 12 inches or so tied into the footing. Keep at least 2 inches of cover over the steel so it does not rust and spall. Skip the rebar and your stairs will crack the first cold winter.

FAQ

How thick should concrete stairs be? If you pour solid, the whole wedge is your thickness. If you use a hollow form with fill, keep the concrete shell 5 to 6 inches thick over the treads and risers.

How many 80 lb bags for concrete steps? For a standard 4-step set at 4 ft wide, about 40 bags. Each 80 lb bag yields 0.60 cubic feet, so divide your total cubic feet by 0.60 and round up.

Can I pour stairs in sections? I do not recommend it. Stairs should go in one continuous pour so they cure as one monolithic unit. Cold joints between steps turn into cracks.

Do concrete stairs need a footing? Yes, a footing below the frost line so they do not heave and separate from the structure. The stair rebar should tie into that footing with dowels.

How much extra concrete should I order? Add about 10 percent to your total for spillage, over-excavation, and uneven subgrade. Running short mid-pour is far worse than a little left over.

Ready to Size Your Pour?

Plug your own width, run, rise, and step count into our free concrete steps calculator and get your exact cubic yards and bag count in seconds. Measure twice, order once, and pour in a single shot.