Concrete Stairs Calculator

Solid concrete steps are a stack of rectangular blocks. The bottom step is one riser tall, the next is two risers tall, and so on, each one tread deep and the full stair width. Adding those blocks gives the volume of a solid stair. Most entry stairs are poured this way, sometimes with a landing at the top. This concrete stairs calculator totals the steps and an optional landing, adds a waste allowance, and converts the result to cubic yards and bags. It also checks your riser height and tread depth against the International Residential Code's limits of a 7¾-inch maximum riser and a 10-inch minimum tread.

For wooden stairs, the stair stringer calculator lays out the stringer. For the slab the steps sit on, use the concrete slab calculator.

How to use the concrete stairs calculator

1. Enter the number of risers, the riser height and the tread depth. To find the riser count, divide the total rise by your target riser height and round up.
2. Enter the stair width.
3. If there is a top landing, enter its depth (front to back). It is assumed to be the full stair width and the full height of the stair plus one riser.
4. Keep 10% extra for form flex and spillage.

Formula

The formula assumes solid steps on grade. Steps poured against a wall or over fill (gravel or rubble in the core) use less concrete.

Worked example

Four steps, 7 in risers, 11 in treads, 4 ft wide, no landing, 10% extra.

1. In feet: riser 0.5833, tread 0.9167.
2. Step volumes: 4 × 0.9167 × 0.5833 × (1 + 2 + 3 + 4) = 2.139 × 10 = 21.39 ft³.
3. With 10%: 23.53 ft³ = 0.87 yd³.
4. In bags: 23.53 ÷ 0.6 = 39.2, so 40 × 80 lb bags.
5. Check: 7 in risers are within the 7¾ in maximum, and 11 in treads exceed the 10 in minimum.

Code limits for residential stairs

The 2021 International Residential Code (section R311.7.5) limits riser height to 7¾ inches and requires treads at least 10 inches deep, measured nose to nose. Within a flight, the largest riser or tread may not exceed the smallest by more than ⅜ inch. Local codes may modify these, and exterior steps often need a landing at the door: the IRC generally requires a landing at least 36 inches deep at exterior doors, with some exceptions. The IRC also requires a handrail on at least one side of flights with four or more risers. Check with your building department before forming.

Saving concrete on tall stairs

On tall stairs, the solid core under the upper steps is mostly wasted concrete. Builders often fill the core with compacted gravel or clean rubble, keeping at least a few inches of concrete around it, or pour the steps as a sloped slab that follows the stair. Both options cut the volume, but they need careful forming and reinforcement. Steps are usually tied to the foundation or a footing with rebar dowels so they don't settle away from the house; see the rebar calculator. For a large pour, ready-mix is usually cheaper and gives a better finish than mixing 40 or more bags by hand.

Caveats and assumptions

• Assumes solid steps resting on grade; fill or a sloped underside reduces the volume.
• Landing volume assumes the landing is the full width and sits at the height of the top step.
• Riser and tread checks use the 2021 IRC; your jurisdiction may differ.
• Bag yields (80 lb ≈ 0.6 ft³, 60 lb ≈ 0.45 ft³) are approximate.

Frequently asked questions

Sources

• ICC — 2021 International Residential Code, Section R311.7.5 Stair treads and risers — maximum riser, minimum tread
• Quikrete — Concrete Calculator and product yields — yield per 80 and 60 lb bag
• Portland Cement Association — concrete construction guidance

This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.