Rebar Calculator
Estimate rebar quantity, length, and weight for concrete reinforcement
Length of the concrete area
Width of the concrete area
On-center spacing
#3=3/8", #4=1/2"
Bars (Length Direction)
—
bars
Bars (Width Direction)
—
bars
Total Rebar Length
—
ft
Total Weight
—
lbs
Estimated Cost
—
USD
How to Use This Calculator
Proper rebar reinforcement prevents cracking and extends the life of your concrete. Our calculator helps you determine the number of bars, total length, and weight needed.
- Measure the length and width of your concrete area
- Choose rebar size based on slab thickness
- Select spacing (18" standard for residential)
- Add 10% for overlaps and waste at joints
AI Insights
Smart analysis for your project
Smart Estimates
Our AI cross-references material costs, regional pricing, and project complexity for more accurate estimates.
Waste Optimization
AI-calculated waste factors based on project type, not flat percentages. Saves 5-15% on material costs.
Best Practices
Recommendations derived from building codes, contractor data, and thousands of completed projects.
Calculation Formula
Bars per direction = (Dimension / Spacing) + 1
Total length = Sum of all bar lengths
Weight = Total length x lbs/ft (by bar size)
Frequently Asked Questions
What size rebar do I need for a concrete slab?
#3 or #4 rebar is standard for residential slabs (4-6" thick). Use #4 for driveways and #5 for commercial.
How far apart should rebar be spaced?
Standard spacing is 18" on center for residential slabs and 12" for driveways. Always overlap bars 15-20x the bar diameter at joints.
Do I need rebar in my concrete slab?
Rebar is recommended for slabs 5" or thicker, driveways, and any slab bearing heavy loads. For 4" patio slabs, wire mesh may be sufficient.