Concrete Stairs Calculator
Estimate the concrete needed to pour a set of solid steps, in cubic feet, cubic yards, and bags, from the step count, rise, run, and width.
Reviewed by the ToolNestr Editorial Team — July 2026
How the concrete stairs calculator works
A solid poured stair is a stack of steps where each tread rests on the mass of every step below it. The bottom step is the tallest block of concrete, and each step up is one rise shorter. Adding those blocks together gives a neat pattern: the total is the width times one step's run times its rise times the sum 1 + 2 + 3 up to the number of steps, which equals N(N+1)/2.
The calculator takes rise and run in inches and width in feet. It multiplies rise by run and divides by 144 to turn the step face into square feet, multiplies by the N(N+1)/2 factor for the stacked steps, then multiplies by the width for cubic feet. Dividing by 27 gives cubic yards, and dividing by the bag yield (0.6 cubic feet for 80 lb, 0.45 for 60 lb) gives the bag count.
Rise and run also drive stair safety. The calculator flags a riser over 7.75 inches or a run under 10 inches, the limits set by the International Residential Code (IRC) for stairs. This assumes fully solid steps; if you pour over compacted fill, your real concrete will be less than the estimate.
Set step geometry
Enter the number of steps and the rise and run of each in inches.
Add the width
Enter how wide the stairs are in feet, measured across the treads.
Check the flag
Watch for the code warning on rise and run, and subtract any fill you plan to use.
The formula explained
Stacked-step factor
factor = N(N+1)⁄2. For 5 steps: 5 × 6 ÷ 2 = 15 — the bottom step counts 5 times, the next 4, and so on.
Volume
V = W × (rise × run ⁄ 144) × factor. With 7″ rise, 11″ run, 4 ft wide: 4 × (77⁄144) × 15 = 32.1 ft³.
Yards and bags
CY = ft³ ÷ 27: 32.1 ÷ 27 = 1.19 cu yd. In 80 lb bags: 32.1 ÷ 0.6 = 54 bags — ready-mix is usually cheaper here.
Worked example
A 3-step porch stoop, 6.5″ rise, 12″ run, 5 ft wide.
Where concrete steps are used
Porch and entry stoops
A short flight of solid steps up to a front door is one of the most common home concrete pours, usually two to five steps to a small landing.
Deck and patio access
Steps connecting a raised deck or patio to the yard take heavy foot traffic, so a solid concrete flight lasts far longer than wood.
Garden and grade steps
Steps set into a slope tame a sloped yard. Because they sit on earth, they are often poured over compacted fill to cut the concrete volume.
Basement and garage steps
Steps down to a basement door or a sunken garage are usually solid concrete for durability and moisture resistance below grade.
Tips for pouring steps
Keep every rise equal
Uneven risers are a trip hazard and a common code failure. Divide the total height by the number of steps so each rise is identical, and keep the difference between the largest and smallest riser under 3/8 inch.
Fill the core to save concrete
For tall flights, form the outside and pour a concrete shell over compacted gravel or rubble fill. The steps stay solid on the surface while using far less concrete than a fully solid pour.
Slope treads to drain
Give each tread a slight forward slope, about 1/4 inch, so rain runs off instead of pooling and freezing. This does not change the volume but greatly extends the life of exterior steps.
Real-world context
A typical front-door stoop shows why the N(N+1)/2 factor matters: 4 steps at 7 in rise, 11 in run, 3.5 ft wide need 3.5 × (7×11/144) × 10 ≈ 18.7 cubic feet — the factor of 10 (not 4) is why a 4-step stoop uses well over twice the concrete of a single equivalent step.
A taller deck stair shows how fast that factor compounds: 7 steps at 6.75 in rise, 12 in run, 4 ft wide come out to a factor of 28 — 4 × (6.75×12/144) × 28 = 63 cubic feet, more than 2.3 cubic yards, at which point ready-mix is clearly the practical choice over dozens of bags.
A short 2-step garden landing shows the other end: 6 in rise, 12 in run, 5 ft wide needs just 5 × (6×12/144) × 3 = 7.5 cubic feet — small enough that filling the core with compacted gravel or rubble first, and pouring only a solid shell over it, can cut the concrete order substantially on a taller version of the same step run.
Common misconceptions
"Doubling the number of steps roughly doubles the concrete." It scales faster than that. Because each step sits on all the steps below it, volume grows with N(N+1)/2, not N — going from 4 steps to 8 steps multiplies the stacking factor from 10 to 36, more than triple, not double.
"Any comfortable-feeling rise and run is fine as long as the steps look even." Code sets hard limits. The IRC caps riser height at 7.75 inches and requires at least a 10-inch tread run specifically because inconsistent or overly steep steps are a documented trip hazard — "looks even" isn't the same as measured and compliant.
Related calculators
Frequently asked questions
How do I calculate concrete for stairs?
For solid steps poured to the ground, add up the stacked step sections: volume equals width times run times rise times N(N+1)/2, where N is the number of steps. This treats each step as sitting on all the steps below it, which is how a solid stair pours.
What are code-compliant rise and run?
The International Residential Code limits riser height to a maximum of 7.75 inches and requires a tread run of at least 10 inches. Comfortable outdoor steps often use a lower rise around 6 to 7 inches with a deeper run. Check your local code for exact limits.
Do these steps need to be solid concrete?
Not always. Many exterior steps are poured over compacted fill or rubble to save concrete, leaving only a shell of concrete on top. This calculator assumes fully solid steps, so if you fill the core, your actual concrete will be less.
Should I add a landing at the top or bottom?
If your steps include a landing or a base pad, calculate that flat slab separately as length times width times thickness and add it to the step volume for the full order.
Sources & references
This tool uses standard formulas and reference values from:
- • American Concrete Institute — ACI 318, Building Code Requirements for Structural Concrete. concrete.org
- • ICC — International Residential Code (IRC), span, footing and framing tables. codes.iccsafe.org
- • APA – The Engineered Wood Association, allowable span and load guidance.
Estimates for planning only. Span, load and code values vary by jurisdiction — verify against your local adopted code and a licensed engineer before building.