A 30×40 building has a 140 ft perimeter footing with four corners.
How it works
Total = run length × bars + a lap at every join and corner. Bars to buy = total ÷ stock length.
Example: 2 #4 bars along 140 ft with 4 corners need 317 ft of rebar, or 17 bars of 20 ft, weighing 212 lb.
At a glance
Same settings as the calculator above, changing only the bars.
| Bars | Rebar | 20 ft bars | Weight |
|---|---|---|---|
| 2 | 317 ft | 17 | 212 lb |
| 3 | 475 ft | 25 | 317 lb |
| 4 | 633 ft | 34 | 423 lb |
Rebar sizes (ASTM A615)
| Bar | Diameter | Weight per ft | 20 ft bar |
|---|---|---|---|
| #3 | 0.375 in | 0.376 lb | 7.52 lb |
| #4 | 0.5 in | 0.668 lb | 13.36 lb |
| #5 | 0.625 in | 1.043 lb | 20.86 lb |
| #6 | 0.75 in | 1.502 lb | 30.04 lb |
| #7 | 0.875 in | 2.044 lb | 40.88 lb |
| #8 | 1 in | 2.67 lb | 53.40 lb |
Common questions
How far apart should rebar be in a slab?
Residential slabs commonly use #3 or #4 bars 12 to 18 inches apart each way, but the spacing should come from your plans or local code.
How much do rebar laps need to be?
Lap length depends on bar size, concrete strength and code. 40 bar diameters is a common rule of thumb: 20 in for #4 bar. Check your plans.
How heavy is rebar?
#3 weighs 0.376 lb/ft, #4 0.668 lb/ft, #5 1.043 lb/ft and #6 1.502 lb/ft under ASTM A615.
Sources
- ASTM A615 bar sizes and weights: https://www.astm.org/a0615_a0615m-22.html