Concrete Steps Calculator

How to calculate concrete for steps

Solid poured steps are modeled as a stack of blocks. The bottom step is a block one riser tall, the second is two risers tall, and so on, each one tread deep and the full width of the stairs. The step volume is width × run × rise × n(n+1)÷2, where n is the number of steps. Three 7-inch risers with 11-inch treads on a 4-ft-wide stair come to 4 × 0.917 × 0.583 × 6 = 12.8 cu ft.

Most entry steps end at a landing or stoop in front of the door. The landing is a block the full height of the stairs (n × rise), the full width, and as deep as you enter. The IRC requires a landing at least 36 inches deep in the direction of travel at exterior doors, so the default uses 36 inches. That landing often holds more concrete than the steps themselves.

The total is multiplied by your waste allowance and divided by 27 for cubic yards. Steps are usually poured with bagged mix or a small ready-mix load; the bag counts use 0.60 cu ft per 80 lb bag and 0.45 cu ft per 60 lb bag. A wider or taller stoop quickly passes a cubic yard, where ready-mix becomes worth pricing.

This is the volume of a solid pour. If you fill the core of a large stoop with compacted gravel or broken concrete, subtract that volume. For code, the IRC limits residential risers to 7-3/4 inches and requires treads of at least 10 inches, and risers within a flight should not vary by more than 3/8 inch.

Where these numbers come from

The formulas and default values in this calculator are based on:

• International Residential Code (IRC) R311.7.5 stair riser and tread limits and R311.3 exterior door landings
• QUIKRETE Concrete Mix No. 1101 technical data sheet for bag yields

These are planning estimates. Check product labels, your local building code, and a licensed contractor before you buy materials or build.