1 · Rebar Quantity — Slab, Footing, Column & Beam
A rebar quantity calculator and concrete rebar calculator for the four common elements: enter dimensions and spacing to get bar counts, total linear feet, weight and pieces. Bar counts use ceil(span ÷ spacing) + 1 so both perimeter bars are included; bar length deducts concrete cover at each end.
Slab — two-way grid
How many rebar for a slab, answered three ways: count, length and weight. Default: the 24 × 20 ft example from the FAQ.
Footing — longitudinal runs + ties
Column — verticals + ties
Beam — top/bottom bars + stirrups
2 · Rebar Weight Estimator
Look up any bar’s rebar weight per foot from the ASTM A615 table, then multiply by your length. Rebar weight per linear foot is the bridge between a bar count and the tonnage on the delivery ticket.
Rebar size chart — diameter, area & weight (ASTM A615)
Nominal dimensions per ASTM A615 Table 1. This rebar weight chart and rebar diameter chart cover the sizes this tool estimates (#3–#11).
| Bar | Diameter (in) | Diameter (mm) | Area (in²) | Weight (lb/ft) | Weight (kg/m) |
|---|---|---|---|---|---|
| #3 | 0.375 | 9.5 | 0.11 | 0.376 | 0.560 |
| #4 | 0.500 | 12.7 | 0.20 | 0.668 | 0.994 |
| #5 | 0.625 | 15.9 | 0.31 | 1.043 | 1.552 |
| #6 | 0.750 | 19.0 | 0.44 | 1.502 | 2.235 |
| #7 | 0.875 | 22.2 | 0.60 | 2.044 | 3.042 |
| #8 | 1.000 | 25.4 | 0.79 | 2.670 | 3.973 |
| #9 | 1.128 | 28.7 | 1.00 | 3.400 | 5.060 |
| #10 | 1.270 | 32.3 | 1.27 | 4.303 | 6.404 |
| #11 | 1.410 | 35.8 | 1.56 | 5.313 | 7.907 |
3 · Grid & Spacing Solver
Enter the slab area and target spacing: bars per direction, steel area per foot of slab, and the rebar lap splice length — the 40×-diameter field rule of thumb (minimum 12 in), clearly labeled as an estimating starting point.
4 · Cost Estimator
Price rebar two ways — by weight ($/lb) or by the piece. Both are labeled estimates: edit the rates for your supplier.
By weight
By the piece
This rebar cost calculator / rebar estimator reports material cost only — no delivery, cutting, bending, tying labor or waste factor. Add your own waste percentage on top.
Rebar FAQ
Worked answers, every number computed by the engine from the 24 × 20 ft slab example above.
How much rebar do I need for a 24x20 ft concrete slab?
For a 24 × 20 ft slab with #5 rebar at 12 in spacing (3 in cover), this rebar quantity calculator gives 46 bars — 21 running the 24 ft direction and 25 running the 20 ft direction — for 981 linear feet total. By hand: bars across a width = ceil(width in inches ÷ spacing) + 1, including both perimeter bars.
How much does that slab rebar weigh?
981 linear feet of #5 rebar × 1.043 lb per foot = 1,023.2 lb, about 0.51 tons. Use the rebar weight calculator tab above for any bar size and any length.
How much does #5 rebar weigh per foot?
The #5 rebar weight per foot is 1.043 lb (0.625 in diameter, 0.31 in² cross-section) per the ASTM A615 rebar weight chart. For comparison, the #4 rebar weight per foot is 0.668 lb — see the full rebar size chart in the weight tab.
What is the diameter of #5 rebar?
#5 rebar is 0.625 in (5/8 in) in diameter. Bar numbers equal eighths of an inch of nominal diameter for sizes #3 through #8 (for example #4 = 4/8 = 1/2 in). Sizes #9 and larger use the ASTM table values: #9 = 1.128 in, #10 = 1.270 in, #11 = 1.410 in — see the rebar diameter chart in the weight tab.
How many pieces of rebar in a slab?
Divide total linear feet by the stock stick length and round up — that is how this rebar pieces calculator works. For the 24 × 20 ft example: 981 ÷ 20 ft = 50 sticks of 20-ft rebar. Common US stock lengths are 20, 40 and 60 ft.
What does the rebar cost?
Two ways to price it, both labeled estimates rather than quotes. By the piece: 50 sticks × $8.50 = $425.00. By weight: 1,023.2 lb × $0.55 per lb = $562.75. Edit the rebar price per foot or per piece in the cost tab for your supplier.
What is the lap splice length for #5 rebar?
The field rule of thumb is 40 bar diameters: 40 × 0.625 in = 25 in (2 ft 1 in) for #5. Never lap less than 12 in, and always confirm the actual lap against your structural drawings — ACI 318 development lengths depend on concrete strength, cover, coating and bar position, so this rebar lap splice length is an estimating starting point, not a design value.
How much rebar for a 100 ft footing?
A 100 ft footing with 4 runs of #4 and #4 ties at 12 in (16 × 8 in section): 400 linear feet longitudinal + 101 ties (2.0 ft each) = 602 linear feet total, weighing 402.1 lb. The rebar overlap length adds extra — count one 40-diameter lap at every stock-length joint.
How much rebar for a 10 ft column?
A 10 ft, 12 × 12 in column with four #6 verticals and #4 ties at 12 in: 40 linear feet of vertical bar + 11 ties (3.0 ft each) = 73 linear feet, 82.1 lb total. Vertical steel size and tie spacing come from the structural design — this column rebar calculator only takes off quantities.
How much rebar for a 20 ft beam?
A 20 ft, 12 × 18 in beam with 2 top + 2 bottom #6 bars and #4 stirrups at 8 in: 80 linear feet longitudinal + 31 stirrups (4.0 ft each) = 204 linear feet, 203.0 lb. This beam rebar calculator reports stirrup count, length and weight separately.
How do I calculate rebar spacing and steel area?
Bars across a width = ceil(width in inches ÷ spacing in inches) + 1 — that is how to calculate rebar counts by hand. Steel area per foot of slab = bar area × 12 ÷ spacing: #5 at 12 in gives 0.31 in² per foot. The rebar spacing calculator tab above does both directions at once.
Can I design the rebar myself with this tool?
No. Structural reinforcement must be designed by a licensed professional engineer — bar size, spacing, laps, hooks and development lengths depend on loads, soil, concrete strength and code provisions this rebar estimator does not evaluate. Use this tool for material takeoffs and learning only.