Concrete Rebar Calculator
Plan a two-way slab grid. Estimate rebar length, stock sticks, weight, and ordering allowance.
Slab Grid
Common slabs
Ready to calculate
Enter slab dimensions or choose a preset.
Last updated June 2, 2026 by our expert review team
Read the Grid Before You Order
| Planning item | Calculator uses | Confirm from drawings |
|---|---|---|
| Grid spacing | Bars in both directions | Bar size and on-center spacing |
| Order length | Grid length plus allowance | Lap splice lengths and bends |
| Stock sticks | Order length divided by stick length | Available stock and cut list |
| Placement | Not auto-designed | Cover, chairs, and supports |
Expert Contributors
Ehsan Ghazanfari
Licensed Structural Engineer
FISE-certified structural engineer with 11+ years designing bridges, retaining walls, and foundations. MSc from Aalto University.
See full profileHawkin
Certified Cost & Estimating Professional
AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.
See full profileUpdated June 2026
How we verify our calculatorsRebar Grid Ordering Guide
Count both grid directions first. Then translate the layout into stock sticks with room for the lap details on your drawings.
The grid count is a takeoff aid. The project design still controls bar size, spacing, cover, supports, and splice details.
Cost per Linear Foot by Size
#3 (3/8")
$0.40 - $0.70 / ft
#4 (1/2")
$0.50 - $0.90 / ft
#5 (5/8")
$0.65 - $1.10 / ft
#6 (3/4")
$0.80 - $1.40 / ft
Steel supplier pricing varies by region and order size. Hardware-store sticks often cost more per foot.
Pro Tips
Start with the reinforcing plan. Bar size, spacing, cover, and splice details come from the project design.
The order length includes a modest allowance for cuts and laps. It is not a replacement for a bar schedule.
Keep bars supported on chairs or bolsters so the grid stays at the specified elevation during the pour.
Use the concrete slab calculator for the concrete volume around the grid.
For continuous footing volume, use the concrete footing calculator.
How the Calculator Works
The calculator counts grid lines in both directions. It uses ceiling logic so the final bay does not exceed the selected spacing. The ordering allowance is applied after the basic grid length.
Lengthwise bars
ceil(width / spacing) + 1
Widthwise bars
ceil(length / spacing) + 1
Order length
grid length x allowance
Quick Reference
- #3 weight
- 0.376 lb/ft
- #4 weight
- 0.668 lb/ft
- #5 weight
- 1.043 lb/ft
- #6 weight
- 1.502 lb/ft
- Typical stock
- 20 ft or 6 m
- Lap details
- use drawings
Slab Grid Examples
Patio
10 x 10 ft, #4, 12 in spacing
242 ft order length, 13 sticks
A small two-way slab grid with 10% allowance.
Driveway section
20 x 12 ft, #4, 12 in spacing
563 ft order length, 29 sticks
The default takeoff. Confirm the structural plan before ordering.
Garage floor
24 x 24 ft, #4, 12 in spacing
1,320 ft order length, 66 sticks
A larger grid where a cut list matters.
Metric pad
6 x 3 m, #4, 30 cm spacing
141.9 m order length, 24 sticks
Uses 6 m stock sticks and 10% allowance.
Concrete Rebar FAQ
What does this calculator estimate?
A two-way slab grid takeoff: grid bars, total length, stock sticks, order weight, and a material planning range.
Does the calculator choose rebar size?
No. Use the project design for bar size, spacing, cover, lap lengths, and placement.
Why is the order length longer than the grid length?
The advanced allowance covers planning room for cuts and lap splices. Use the drawings for the actual splice schedule.
Why are there bars in both directions?
A slab grid is counted as two sets of bars. One set runs lengthwise and one runs widthwise.
Can I use this for footings or walls?
Use it only as a rough length check. Footings, walls, hooks, and bends need a project-specific bar schedule.
What stock length should I enter?
Use the straight stick length your supplier sells, often 20 ft or 6 m. Confirm before placing the order.
Rebar Planning Mistakes
Counting one direction only
A slab grid has lengthwise and widthwise bars. Count both sets before adding an allowance.
Treating the allowance as a splice design
Use it for ordering room only. Lap lengths and locations belong on the drawings.
Leaving bars unsupported
Use the specified chairs or supports so placement does not shift during the pour.
Assuming every project uses the same grid
Loads, slab design, subgrade, and local requirements can change the reinforcement plan.
Important Disclaimer
These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.