🧱 Concrete Stair Calculator

The Concrete Stair Volume Formula

Poured concrete steps form a solid staircase wedge. Viewed from the side, the concrete fills a series of stacked rectangles — the bottom step carries the tallest column of concrete, the top step the shortest. That side-profile area is:

This calculator assumes solid poured steps. If you are building over a fill core (rubble or foam) to save concrete, subtract that core volume from the total.

Bags vs. Ready-Mix

• Bags: an 80 lb bag yields ~0.60 cu ft; a 60 lb bag ~0.45 cu ft. Practical for a 3–4 step stoop.
• Ready-mix: once you pass ~1 cubic yard (about 45 bags of 80 lb), a truck is cheaper and far less mixing. Most suppliers have a short-load minimum.

Need slab or footing concrete too? Use our concrete calculator and concrete cost calculator.

Base, Rebar & Forms

• Base: 4–6 in of compacted gravel under the steps and footing.
• Reinforcement: #4 rebar and wire mesh tied into a footing that reaches below the frost line.
• Forms: build rigid riser forms; the run of each step usually slopes about 1/8 in per foot forward so water sheds off.

How many steps for a given rise?

Divide total rise by 7.5 inches and round up to get the number of risers, then divide the total rise by that number for the exact riser height. A flight has one fewer tread than risers, because the top landing serves as the last tread — missing that is the most common stair-framing error. Codes commonly cap risers at 7¾ in and require treads of at least 10 in; your local code governs.

Frequently Asked Questions

How do you calculate concrete for stairs?

Concrete stairs form a solid staircase wedge. The cross-section area equals the number of steps times (number of steps plus one), divided by two, times the riser height times the tread run. Multiply that area by the stair width, then convert to cubic yards by dividing by 46,656 cubic inches per yard.

How much concrete do I need for 3 steps?

For three 36 inch wide steps at a 7 inch riser and 11 inch run, you need about 0.36 cubic yards (roughly 9.6 cubic feet), or about 17 bags of 80 lb or 22 bags of 60 lb mix. Enter your exact dimensions above for a precise number.

How many bags of concrete for concrete steps?

An 80 lb bag yields about 0.6 cubic feet and a 60 lb bag about 0.45 cubic feet. Divide your total cubic feet (with waste) by those figures to get the bag count. For anything over about a cubic yard, ready-mix is usually cheaper than bags.

Should I use bags or ready-mix for concrete stairs?

Small stoops of 3 to 4 steps are fine with bagged concrete. Once you pass roughly 1 cubic yard (about 45 bags of 80 lb), a ready-mix delivery is cheaper and far less work.

Do concrete stairs need rebar?

Yes. Poured concrete steps should be reinforced with #4 rebar and wire mesh, tied into the footing, to prevent cracking and settling. Steps also need a compacted gravel base and a footing below the frost line.

What is the standard rise and run for concrete steps?

Concrete steps typically use a 6 to 7 inch riser and an 11 to 12 inch tread. The IRC caps residential risers at 7.75 inches and requires at least a 10 inch tread.