⚠️ Estimates only. Verify with structural drawings and local codes.
📌 Quick Answer: A steel rebar calculator determines the total weight, linear feet, and cost of reinforcing bars. For a #4 rebar (0.668 lbs/ft), a 20 ft bar weighs 13.36 lbs. Ten bars = 133.6 lbs, costing ~$113 at $0.85/lb. Use the calculator above for your exact bar size, quantity, and project needs.
📋 Key Takeaways — Steel Rebar at a Glance
Rebar weight = Length (ft) × Weight/ft × Quantity
#4 rebar: 0.500" dia, 0.668 lbs/ft (most common residential)
Bar number ÷ 8 = nominal diameter in inches (#4 = 0.5")
Standard stock lengths: 20 ft and 40 ft
10% waste factor standard for laps and cuts
2026 US pricing: $0.60-$1.20/lb ($700-$1,200/ton)
ℹ️ Over 50,000 contractors, engineers, and DIY builders use this steel rebar calculator 2026. Get exact weight, cost, and bar quantities for slabs, beams, columns, and footings using ASTM A615 sizes.
💡 Planning Tip: Add 10% waste for standard laps. For complex layouts or heavy splicing, use 15%. Always order in full stock lengths (20 ft or 40 ft) to minimize cutting waste.
📊 ASTM A615 Standard Rebar Sizes & Weights
Bar Size
Nominal Diameter
Weight (lbs/ft)
Weight (20 ft bar)
Common Use
#3
0.375"
0.376
7.52 lbs
Stirrups, ties, light slabs
#4
0.500"
0.668
13.36 lbs
Residential slabs, footings
#5
0.625"
1.043
20.86 lbs
Beams, heavier slabs
#6
0.750"
1.502
30.04 lbs
Columns, heavy beams
#8
1.000"
2.670
53.40 lbs
Heavy structural, commercial
#10
1.270"
4.303
86.06 lbs
Large foundations, bridges
👨 Mike — Residential Slab, Texas
Project: 20 ft × 20 ft slab | #4 @ 12" OC | 2 directions
✅ "Perfect for budgeting. The 10% waste factor was spot on for our laps."
What is a Steel Rebar Calculator and How Does It Work?
A steel rebar calculator is an essential construction tool that determines the total weight, linear footage, and cost of reinforcing bars for concrete projects. Our steel rebar calculator 2026 uses ASTM A615 standard weights to provide accurate estimates for slabs, beams, columns, and footings. The calculator answers the key questions: How much does my rebar weigh? How many bars do I need? What will it cost?
How does the rebar weight calculator work? Select your bar size (#3 through #10), enter the length of each bar and the quantity, choose your project type, add a waste factor for laps, and enter the price per pound. The rebar cost estimator instantly shows total weight, total linear feet, weight per bar, cost per bar, and total cost.
Rebar Weight Formula (ASTM A615)
Total Weight (lbs) = Length (ft) × Weight per foot (lbs/ft) × Quantity × Waste Factor
Weight per foot is fixed by ASTM standard for each bar size. The bar number divided by 8 equals the nominal diameter in inches: #4 ÷ 8 = 0.5 inch.
How to Calculate Rebar for a Slab
For a rectangular slab with rebar in both directions:
Bars running width: (Length ÷ Spacing) + 1. Multiply by slab width for linear feet.
Bars running length: (Width ÷ Spacing) + 1. Multiply by slab length for linear feet.
Example: 20 ft × 20 ft slab with #4 @ 12" OC:
Bars running width: (20 × 12 ÷ 12) + 1 = 21 bars × 20 ft = 420 ft
Bars running length: 21 bars × 20 ft = 420 ft
Total: 840 linear feet → 840 × 0.668 = 561 lbs (before waste).
2026 US Rebar Pricing
Retail / small quantities: $0.85-$1.20 per lb (20 ft sticks at home centers).
Bulk / contractor pricing: $700-$1,200 per ton ($0.35-$0.60 per lb) depending on region and quantity.
Regional variations: Northeast and West higher, South and Midwest lower. Grade 60 is standard; Grade 75/80 costs more.
Rebar Grade and Specification
ASTM A615 is the standard specification for deformed and plain carbon-steel bars for concrete reinforcement. Grade 60 (60,000 psi yield) is the most common in US construction. Grade 40 is used for light residential, Grade 75/80 for heavy structural. Always verify the grade required by your structural drawings.
❓ Frequently Asked Questions
How do I calculate rebar weight?
Rebar weight (lbs) = Length (ft) × Weight per foot (lbs/ft) × Quantity. For example, #4 rebar weighs 0.668 lbs/ft. A 20 ft #4 bar weighs 13.36 lbs. Use our steel rebar calculator for exact results.
What are the standard US rebar sizes?
ASTM A615 standard sizes: #3 (0.376 lbs/ft), #4 (0.668 lbs/ft), #5 (1.043 lbs/ft), #6 (1.502 lbs/ft), #8 (2.670 lbs/ft), #10 (4.303 lbs/ft). The bar number divided by 8 equals the nominal diameter in inches (#4 = 4/8 = 0.5 inch).
How many pieces of rebar do I need for a slab?
Divide slab width by rebar spacing and add 1. Example: 10 ft wide slab at 12-inch spacing = (10 × 12 ÷ 12) + 1 = 11 bars. Multiply by length for total linear feet. Use our rebar calculator for exact quantities.
How much does rebar cost in 2026?
US rebar prices in 2026 range from $0.60-$1.20 per lb depending on bar size, grade, and region. A 20 ft #4 bar costs approximately $8-$16. Bulk pricing (tons) ranges $700-$1,200 per ton.
What is the difference between #4 and #5 rebar?
#4 rebar has a 0.5 inch diameter and weighs 0.668 lbs/ft. #5 rebar has a 0.625 inch diameter and weighs 1.043 lbs/ft. #5 is 56% heavier and used for heavier structural loads.
How do I calculate rebar for a rectangular footing?
Calculate bars in both directions: (Length ÷ Spacing) + 1 for bars running the width, and (Width ÷ Spacing) + 1 for bars running the length. Multiply each by the corresponding dimension to get linear feet.
💡 Expert Tips for Rebar Planning
Tip #1: Always add 10% waste for standard laps and cuts. For complex layouts or heavy splicing, use 15%.
Tip #2: Order in full stock lengths (20 ft or 40 ft) to minimize cutting waste. Custom-cut lengths cost more.
Tip #3: Verify rebar grade (40, 60, 75, 80) with your structural drawings. Grade 60 is standard for most US residential and commercial work.
Tip #4: Don't forget tie wire, chairs, and bar supports — these are separate from rebar cost but essential for proper placement.
🔩 Still Asking "How Much Rebar Do I Need?"
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🛡️ CDCalculators proprietary steel rebar calculator 2026 — data sources: ASTM A615, CRSI Manual of Standard Practice, 2026 US market pricing. Last updated October 22, 2026. Disclaimer: Estimates only. Verify with structural drawings and local building codes.