Concrete Stair Calculator
Calculate cubic yards of concrete for poured stairs. Includes form dimensions, rebar requirements, and material quantities.
How It Works
Enter the total rise, number of steps, stair width, and tread depth. The calculator computes the total volume of concrete needed in cubic yards by calculating each step as a rectangular section plus the base slab. It accounts for the stair profile geometry (each step adds a rectangular block on top of the one below). Results include: total concrete volume, form lumber needed, rebar quantity, and estimated material cost.
Frequently Asked Questions
How much concrete do I need for stairs?
Concrete volume depends on the number of steps, their dimensions, and stair width. A typical 3-step entry stair (36" wide) needs about 0.3-0.5 cubic yards. This calculator computes the exact volume based on your measurements.
Do concrete stairs need rebar?
Yes, concrete stairs should be reinforced with #4 rebar (1/2" diameter) placed in a grid pattern. Typical spacing is 12" on center in both directions, placed 2-3" from the bottom of the slab. Steps themselves can use mesh reinforcement.
How thick should the concrete base be under stairs?
The base slab under concrete stairs should be at least 4" thick, poured on 4-6" of compacted gravel. In cold climates, the base should extend below the frost line or bear on a frost-protected foundation.
What concrete mix should I use for stairs?
Use a minimum 4,000 PSI concrete mix for stairs. For exterior stairs, use air-entrained concrete (5-7% air content) for freeze-thaw resistance. A standard 80-lb bag of concrete makes about 0.6 cubic feet.