Formula and input notes
Grid length = bars across width × slab length + bars across length × slab width, then add lap and waste allowance
| Input | Practical note |
|---|---|
| Bar spacing | This is the Rebar Calculator layout value for bar spacing; confirm whether the drawing specifies clear or on-center spacing. |
Worked rebar example
Rebar Calculator example: The grid uses 9 bars running 21.4 ft and 16 bars running 10.9 ft. After 15% lap/waste allowance, total length is 422.05 ft, or 22 20-ft sticks.
Read total bar length and 20-foot stick count
Use linear feet and 20-ft-stick count as a rough purchasing check only; a bar bending schedule should control fabricated reinforcement.
Laps, supports, edge bars, and reinforcing design
Cover, exact edge offsets, laps, hooks, dowels, openings, chairs, bar mark lengths, stock-length optimization, and multiple mats affect the final schedule.
Questions specific to this calculation
Does the grid total include laps, supports, or edge bars?
Enter slab plan dimensions and the maximum on-center spacing for an orthogonal grid. The calculation includes a bar at both limits of each direction.