Concrete Calculator for Steps: How to Measure Complex Stairs

Steps are notoriously difficult to calculate because they are essentially a series of overlapping rectangles and triangles. If you get the math wrong, you'll end up with a huge mess on pour day. Most DIYers under-estimate steps by as much as 30%.

The Anatomy of a Step

To calculate correctly, you need to understand two terms: the Run (the flat part you walk on) and the Rise (the vertical height of each step). You also need to know if the steps are "solid" or if they are sitting on top of an existing slope.

The "Wedge" Calculation Method

The most accurate way to calculate a set of stairs is to treat the entire staircase as one large rectangular block and then divide by two (the wedge), and then add the "landing" at the top.

The Formula: (Total Length x Total Width x Total Height) / 54 (This gives you the volume of the triangular wedge). Then add the volume of your top landing (L x W x H / 27).

Real-World Example

Imagine 5 steps, each with a 7-inch rise and a 12-inch run, and a 4-foot wide staircase.

• Total Rise = 35 inches (2.91 feet)
• Total Run = 60 inches (5 feet)
• Width = 4 feet
• (2.91 x 5 x 4) / 54 = 1.07 cubic yards for the stairs alone.

Form Pressure Warning

Because steps are vertical, the "head pressure" of the concrete is much higher than a flat slab. Your riser boards must be braced incredibly well. If a bottom riser blows out during the pour, all the concrete from the steps above will come rushing out of the bottom like a landslide.

Getting step math right is hard. Use our stair concrete calculator logic to ensure your next set of steps is perfect.