Construction Calculator
Rebar Calculator
Estimate rebar pieces, spacing, total linear feet, stick count, weight, waste, lap allowance, and material cost for slabs, patios, driveways, footings, and concrete reinforcement grids.
Best for
Slabs + footings
Outputs
Feet, weight, cost
Useful for
DIY + pros
Rebar size basics
Rebar numbers match nominal diameter in eighths of an inch. A #4 bar is about 4/8 inch, or 1/2 inch. A #5 bar is about 5/8 inch.
Common residential choice
#4 rebar at 12–24 in. spacing
Always verify project requirements, local code, and engineering specs.
Calculate rebar
Estimate reinforcement quantities for a slab grid, footing runs, or a custom total linear-foot order. Adjust rebar size, spacing, stock length, lap allowance, waste, and pricing.
Rebar estimate
Sticks to buy
19
Based on 20 ft stock length, 10% waste, and 5% lap allowance.
This is a material estimate only. Structural reinforcement design, spacing, cover, lap length, and bar size should follow project plans, local code, and engineering requirements.
Rebar size, thickness, and weight chart
Use this chart to compare common rebar sizes. Smaller numbers are lighter and easier to handle. Larger bars add more steel weight and are typically used for heavier structural work.
| Rebar size | Nominal diameter | Approx. weight | Common use |
|---|---|---|---|
| #3 | 3/8 in | 0.376 lb/ft | Small pads, light slabs, ties, repairs |
| #4 | 1/2 in | 0.668 lb/ft | Residential slabs, patios, sidewalks, light driveways |
| #5 | 5/8 in | 1.043 lb/ft | Driveways, heavier slabs, footings, walls |
| #6 | 3/4 in | 1.502 lb/ft | Heavier footings, foundation work, structural projects |
| #7 | 7/8 in | 2.044 lb/ft | Larger engineered concrete work |
| #8 | 1 in | 2.670 lb/ft | Heavy structural and commercial reinforcement |
For beginners
Rebar should be placed inside the concrete, not at the very bottom and not touching the soil or forms. Use chairs, dobies, or supports so concrete can surround the steel.
For experienced workers
Add waste, lap allowance, stock length, and price per stick to turn a quick spacing layout into a more realistic material order estimate.
Important note
This calculator estimates material quantity. It does not replace engineered reinforcement design, local code requirements, or project-specific structural specifications.
Rebar calculator FAQs
What does #4 rebar mean?
#4 rebar is approximately 4/8 inch, or 1/2 inch, in nominal diameter. The same pattern applies to common U.S. bar sizes.
How much does #4 rebar weigh?
#4 rebar weighs about 0.668 pounds per linear foot. A 20-foot stick weighs about 13.36 pounds before ties, waste, or handling extras.
What spacing should I use?
Common slab spacing may be 12, 16, 18, or 24 inches on center. The correct spacing depends on slab thickness, load, soil, climate, local code, and engineering requirements.
Do I need lap splices?
If bars must be joined end-to-end, overlap may be required. Actual lap length depends on engineering specs, bar size, concrete strength, bar grade, and project conditions.