#4 Rebar Calculator — Bar Count, Weight & Spacing
Estimate #4 (1/2-inch) rebar bar count, total weight, and grid spacing for a slab or footing. This is the default residential concrete reinforcement size.
Enter Dimensions
Add 10% for standard cuts and overlaps
Results
Bars Needed
38bars
Total Lineal Feet
608lin ft
Total rebar length including waste
Total Weight
406lb
#4 rebar weight per CRSI
Slab Area
240sq ft
Editorial Standards
Each calculator is reviewed for formula accuracy, unit consistency, and alignment with current U.S. building practices before publication. We verify outputs against published engineering references and real-world project data. Learn more about our methodology.
#4 rebar (1/2 inch diameter) is the workhorse of residential concrete construction. It's used in slabs on grade, light footings, free-standing CMU walls, and most lightly-loaded structural applications. At ~$0.50 per linear foot, it's the cost-effective choice when load calculations don't demand a heavier bar.
This calculator estimates #4 piece count, total linear feet, and total weight. For other bar sizes, see the parent Rebar Calculator or the #5 Rebar Calculator.
How to Estimate #4 Rebar
Bars per Direction = ⌈Dimension ÷ Spacing⌉ + 1. Total LF = (Bars × Length) per direction summed. Weight = LF × 0.668 lb.
#4 Rebar Quick Reference
- Diameter: 1/2 inch (0.500 in)
- Weight: 0.668 lb/ft (13.36 lb per 20 ft stick)
- Yield strength: 60,000 psi (Grade 60)
- Min bend dia: 3 in (6 × bar dia)
- Class B lap splice: 20 in (40 × bar dia)
- Standard stock: 20 ft or 40 ft sticks
- Cost: ~$0.50-0.70 per LF (2025)
Frequently Asked Questions
What is #4 rebar?
#4 rebar is 1/2 inch nominal diameter deformed bar — the most common residential reinforcement size. ASTM A615 standard, typically 60,000 psi yield strength (Grade 60). Weight: 0.668 lb per linear foot.
How much does #4 rebar cost?
$0.45-$0.70 per linear foot at most U.S. suppliers in 2025, depending on volume and region. A 20 ft stick runs $9-14. By the ton: ~$700-1000 delivered to a residential site.
How many #4 bars per 100 sq ft slab?
At 12 inch on-center grid (both directions): 100 sq ft × 2 bars per sq ft = 200 linear feet of #4. That's 10 sticks of 20 ft, total weight ~134 lb.
Can #4 rebar replace #5 rebar?
Only by tightening spacing. To match #5 at 12 inch OC (0.31 sq in steel area per ft): need #4 at ~7 inch OC. Or use 2 layers of #4 at 12 inch OC for slabs over 8 inches thick.
What is the bend radius of #4 rebar?
Minimum 90° hook inside diameter is 6 × bar diameter = 3 inches for #4. Standard hook leg length per ACI 318: 12 × bar diameter = 6 inches minimum.
Looking for the general calculator?
Calculate rebar quantity, spacing, and total weight for concrete slabs, footings, and walls. Covers #3 through #8 bar sizes using CRSI published weight tables.
Open the Rebar Calculator: Bar Count & Weight →