Rebar Weight and Size Calculator
Calculate weight, quantity, and specifications for reinforcing steel bars
Enter Your Rebar Details
#4 (13M): 0.5" diameter,0.668 lbs/ft
Total linear feet of rebar needed
For cutting waste and lap splices
Typical: $0.50-$1.00/lb
Quick Answer
The most common residential rebar sizes are #4 (1/2") and #5 (5/8"). #4 rebar weighs 0.668 lbs per foot and #5 weighs 1.043 lbs per foot. Standard bars are 20 feet long. For 100 feet of #4 rebar, expect about 67 pounds plus 5-10% for waste and splices.
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Complete Rebar Size Chart
| Size | Diameter (in) | Diameter (mm) | Weight (lbs/ft) | Weight (kg/m) |
|---|---|---|---|---|
| #3 (10M) | 0.375 | 9.5 | 0.376 | 0.56 |
| #4 (13M) | 0.5 | 12.7 | 0.668 | 0.994 |
| #5 (16M) | 0.625 | 15.9 | 1.043 | 1.552 |
| #6 (19M) | 0.75 | 19.1 | 1.502 | 2.235 |
| #7 (22M) | 0.875 | 22.2 | 2.044 | 3.042 |
| #8 (25M) | 1 | 25.4 | 2.67 | 3.973 |
| #9 (29M) | 1.128 | 28.7 | 3.4 | 5.06 |
| #10 (32M) | 1.27 | 32.3 | 4.303 | 6.404 |
| #11 (36M) | 1.41 | 35.8 | 5.313 | 7.907 |
| #14 (43M) | 1.693 | 43 | 7.65 | 11.38 |
| #18 (57M) | 2.257 | 57.3 | 13.6 | 20.24 |
Understanding Rebar Numbers
The bar number indicates diameter in 1/8" increments. #4 = 4/8" = 1/2", #5 = 5/8", etc. Metric designations (M) show nominal diameter in millimeters. Standard bars are 20 feet long (6.1m).
Which Rebar Size to Use
#3 Rebar (3/8")
Light duty applications
- • Patios and walkways
- • Decorative concrete
- • Temperature steel
- • Stirrups in beams
#4 Rebar (1/2")
Most common residential
- • Slabs on grade
- • Footings (light)
- • Driveways
- • Garage floors
#5 Rebar (5/8")
Standard structural
- • Foundation walls
- • Structural footings
- • Retaining walls
- • Pool shells
#6 Rebar (3/4")
Heavy structural
- • Structural columns
- • Major footings
- • Bridge components
- • Commercial foundations
#7-#8 Rebar
Commercial/industrial
- • Large beams
- • Industrial floors
- • Highway bridges
- • High-rise structures
#9-#18 Rebar
Heavy infrastructure
- • Major bridges
- • High-rise cores
- • Dam construction
- • Heavy industrial
Lap Splice Requirements
When rebar lengths need to be joined, the bars must overlap (lap splice) by a minimum length to transfer forces. The required lap length depends on bar size, concrete strength, and whether the steel is in tension or compression.
| Bar Size | Min. Tension Lap (40db) | Min. Compression Lap (30db) |
|---|---|---|
| #3 | 15" | 12" |
| #4 | 20" | 15" |
| #5 | 25" | 19" |
| #6 | 30" | 23" |
| #7 | 35" | 27" |
| #8 | 40" | 30" |
* Based on Grade 60 rebar and 3,000 PSI concrete. Actual requirements may vary - always follow engineering specifications. db = bar diameter. 40db = 40 times the bar diameter.
Weight Calculation Formulas
Basic Formula
Weight = Length × Weight/ft
Example (#4 rebar):
100 ft × 0.668 lbs/ft
= 66.8 pounds
Theoretical Formula
W = (d² / 533.4) lbs/ft
Where d = diameter in 1/8"
#4: (4² / 533.4) = 0.030
× 22.26 = 0.668 lbs/ft
Quick Reference: 20' Bar Weights
Frequently Asked Questions
What does #4 rebar weigh per foot?
#4 rebar weighs 0.668 pounds per foot (0.994 kg/m). This is one of the most commonly used sizes for residential concrete reinforcement including slabs, driveways, and light footings. A standard 20-foot bar weighs approximately 13.36 pounds.
What is the diameter of #5 rebar?
#5 rebar has a diameter of 5/8 inch (0.625") or 15.9mm. The bar number corresponds to the diameter in eighths of an inch, so #5 = 5/8 inch. It weighs 1.043 lbs per foot and has a cross-sectional area of 0.31 square inches.
How do I calculate rebar weight?
Multiply the total length of rebar (in feet) by the weight per foot for the selected bar size. For example: 100 feet of #4 rebar = 100 × 0.668 = 66.8 pounds. Always add 5-10% extra for cutting waste and lap splices at joints.
What rebar size should I use for a residential slab?
For residential slabs on grade (4-6 inches thick), #4 rebar (1/2" diameter) is the most common choice, typically placed on 18" to 24" centers in a grid pattern. For footings and structural elements, #5 rebar is often specified. Always follow engineering specifications or local building codes for your specific project.
What is the standard length of rebar?
Standard rebar length is 20 feet (6.1 meters). Longer lengths (40' or 60') are available for commercial projects but require special handling, transportation, and equipment for placement. Rebar can also be ordered cut to custom lengths from suppliers.
How much overlap is required for rebar splices?
Lap splice length is typically 40 bar diameters (40db) for bars in tension. For #4 rebar (1/2" diameter), this equals 20 inches minimum. For #5 rebar (5/8"), it's 25 inches. Compression splices can be shorter (typically 24-30 bar diameters). Always verify with project specifications.
What is the difference between imperial and metric rebar sizes?
Imperial sizes (#3-#18) use bar numbers that represent diameter in 1/8" increments. Metric sizes (10M-57M) use the nominal diameter in millimeters. Common equivalents: #4 (12.7mm) ≈ 13M, #5 (15.9mm) ≈ 16M, #6 (19.1mm) ≈ 19M.
How much does a bundle of rebar weigh?
Standard rebar bundles contain various quantities depending on bar size and supplier. #4 bundles typically contain 50 pieces (20' each) weighing about 668 lbs total. #5 bundles with 50 pieces weigh about 1,043 lbs. Smaller quantities are available for residential and retail purchase.
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Dr. Snezana Lawrence
Mathematical Historian | PhD from Yale
Dr. Lawrence is a published mathematical historian with a PhD from Yale University. She ensures mathematical precision and accuracy in all our calculations, conversions, and academic score calculators. Her expertise spans computational mathematics and educational assessment.
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