Concrete Stairs Calculator
Calculate concrete, rebar, and total cost for your stairs project per IRC R311.7 building codes.
Last updated: January 15, 2026
Enter Stair Details
inches
💡 Vertical height of each step. Max 7¾" per IRC code (comfortable: 7")
inches
💡 Horizontal depth of each step. Min 10" per IRC code (comfortable: 11")
Min 36" per IRC code (residential)
inches (4-6" recommended)
Thickness of the step tread (the part you step on)
inches (4" typical)
Thickness of side walls (if building enclosed stairs)
Main + temperature rebar — best strength and crack control
For DIY only — most stairs use ready-mix delivery
Results
IRC Code: Compliant
Rise: ✓ 7" (max 7¾")
Run: ✓ 11" (min 10")
Width: ✓ 36" (min 36")
Concrete Needed
0.57 cu yd
includes 10% waste
Total Rise
42" (3.5 ft)
Total Run
66" (5.5 ft)
Tread Area
16.5 sq ft
Weight
1.04 tons
Reinforcement
Main Rebar (#4):7 bars × 3.0 ft
Temperature Rebar (#3):3 bars × 5.5 ft
Total Weight:20.23 lbs
Cost Estimate
Concrete:$84.79
Labor:$198
Reinforcement:$24.75
Total:$307.54
Shopping Tips
- • 0.57 cu yd — order 1 truck minimum (short load fee $50-100 may apply)
- • Main Rebar (#4): 7 bars × 3.0 ft = 21.0 ft total — buy 2 × 20ft bars (cut to 3.0ft pieces, 6 per bar)
- • Temperature Rebar (#3): 3 bars × 5.5 ft = 16.5 ft total — buy 1 × 20ft bars (cut to 5.5ft pieces, 3 per bar)
- • Rebar available at Home Depot/Lowe's (standard: 20ft bars)
How to Use This Calculator
- Select your stair type — Interior, exterior, entry, or basement. The calculator will suggest IRC-compliant dimensions.
- Enter number of steps — Count the total steps from bottom to top landing.
- Set step height and depth — Step height (rise) is the vertical height of each step, step depth (run) is the horizontal depth. IRC code: max 7¾" height, min 10" depth.
- Enter width — Minimum 36" per IRC code for residential stairs.
- Add reinforcement — Rebar is required for structural support. #4 rebar at 12" spacing is standard.
- Get your estimate — Review concrete volume, rebar requirements, and total cost. Check IRC compliance before building.
How We Calculate
Concrete Volume = Tread Area × Throat Thickness + Sidewall Volume
Tread Area = Run × Width × Number of Steps
IRC R311.7 Requirements
- • Maximum Rise: 7¾" per step
- • Minimum Run: 10" per step
- • Minimum Width: 36" (residential)
- • Rise Variation: ≤ 3/8" between steps
- • Run Variation: ≤ 3/8" between steps
Comfort Formula
- • 2R + T = 24-25" (most common)
- • R = Rise, T = Tread (Run)
- • Example: 7" rise + 11" run = 25" ✓
- • Comfortable: 7" rise, 11" run
- • Exterior: 6-6.5" rise, 12" run
Example: 6-Step Interior Stair
- Steps: 6
- Rise: 7" per step
- Run: 11" per step
- Width: 36" (3 ft)
- Throat: 5"
- Tread Area: 11" × 36" × 6 = 198 sq ft
- Volume: 198 × 5" = 0.6 cu yd
- With waste: 0.6 × 1.1 = 0.7 cu yd
Calculations based on IRC 2021 R311.7 (International Residential Code) stair requirements. Learn more