Rebar Calculator for Slabs and Footings
A 240 ft run of #4 rebar needs 12 bars. Bar sizes #3 through #8 are supported, the range most often used in home slab, footing, and wall work.
You need
12 bars
240 lin ft (#4 rebar) · 160 lb
(#4 bars @ 20 ft)
Prices for: United States (national average)
Data: wages May 2025 · material: Census baseline, index-adjusted to August 2026
Estimated cost (low confidence)
$543 – $1,080
typical ≈ $811
Installed rebar prices rest on limited public data (a single calibration source). Treat the cost estimate as a rough guide — the quantity above is the reliable part.
Cost breakdown
Mobilization (site setup & delivery) (estimate)$335 – $670 (typical ≈ $500)
- ESTIMATEConcreteCostCalc estimate (no public data available) · Data: September 2026
#4 rebar material$97 – $190 (typical ≈ $146)
- SOURCEDASTM A615 standard rebar weight table (physical specification, not market pricing) · ASTM A615 · Data: n/a (physical specification, not a time series)
- ESTIMATEConcreteCostCalc estimate (no public data available) · Data: September 2026
- CALIBRATEDPublished home-improvement cost guides (used for calibration only) · Data: 2026
Labor & placement$111 – $220 (typical ≈ $165)
- CALIBRATEDPublished home-improvement cost guides (used for calibration only) · Data: 2026
- SOURCEDDerived by ConcreteCostCalc from U.S. Bureau of Labor Statistics — Occupational Employment and Wage Statistics (national estimate: employment-weighted average across 393 metro areas; not a BLS-published national figure) · Data: May 2025 · Level: national
- SOURCEDU.S. Bureau of Labor Statistics — Employer Costs for Employee Compensation, Construction (NAICS 23, private industry) · Data: Q2 2026 · Level: national
- CALIBRATEDDerived by ConcreteCostCalc from U.S. Census Bureau — 2022 Economic Census, NAICS 238110 (Poured Concrete Foundation and Structure Contractors) · Data: 2022 (Census EC2223BASIC) / 2026-Q2 (ECEC) · Level: national
What drives rebar quantity and cost
Rebar sizing is mostly arithmetic. Once you know a run’s total length and the bar size, the stick count, the linear footage, and the total weight all follow from standard bar sizes. This rebar calculator leads with those numbers, since they are the solid part of the page. An installed-cost estimate sits below, marked as a rough guide.
Bar sizes
Rebar is sold by a number tied to its width in eighths of an inch: a #4 bar is about half an inch across, a #6 bar about three-quarters of an inch, and bigger bars weigh more per foot. This rebar estimator covers bar sizes #3 through #8, the range most often used in home slab, footing, and wall work. Each size has a fixed weight per foot set by the ASTM A615 standard, a physical spec that does not shift by region or change over time the way a wage does. This rebar calculator applies one flat national material rate here, with no regional shift.
From length to bar count
Enter a total run length and bar size, and the tool turns that into a stick count, plus the total linear footage and weight. This tool also handles a two-way grid: bars set in both directions across a slab, spaced at a fixed gap. The table below works through a few common panel sizes and gaps, so you can see how fast bar count and weight grow as the gap tightens.
Why the cost estimate carries a lower-confidence flag
The dollar figure under the quantity numbers adds the same parts every other job page uses: a flat setup fee, the rebar itself, and labor to place and tie the bars. Every number on this site carries a label, sourced, calibrated, or an estimate, and the labor rate behind this page’s cost figure leans on one source. That is thinner proof than most of the other job pages’ labor rates rest on. This rebar calculator keeps the quantity numbers above and the cost figure below apart, since the quantity you need is the solid part of this page.
Rebar as part of a larger pour
If you are sizing rebar for a slab, driveway, or patio you are also pricing on this site, the pad calculator, driveway cost calculator, and patio cost calculator each add a rebar-grid option. That option folds an estimated rebar cost into that job’s total, so you do not have to size and add rebar on your own.
Rebar quantity reference
| Panel | Spacing | Bars (both ways) | Total length | Weight |
|---|---|---|---|---|
| 10×10 ft | 12 in o.c. | 22 | 220 lin ft | 147 lb |
| 10×10 ft | 16 in o.c. | 16 | 160 lin ft | 107 lb |
| 10×10 ft | 18 in o.c. | 14 | 140 lin ft | 94 lb |
| 20×20 ft | 12 in o.c. | 42 | 840 lin ft | 561 lb |
| 20×20 ft | 16 in o.c. | 32 | 640 lin ft | 428 lb |
| 20×20 ft | 18 in o.c. | 28 | 560 lin ft | 374 lb |
| 24×24 ft | 12 in o.c. | 50 | 1200 lin ft | 802 lb |
| 24×24 ft | 16 in o.c. | 38 | 912 lin ft | 609 lb |
| 24×24 ft | 18 in o.c. | 34 | 816 lin ft | 545 lb |
Two-way #4 grid, measured edge to edge, with no allowance for concrete cover or lap splices. Bar count and length come from geometry alone; weight is derived from the ASTM A615 standard rebar weight table the calculator above uses. U.S. national average material pricing.
Rebar for a concrete slab
Sizing slab rebar takes two more inputs beyond diameter: a panel's span and the spacing between bars. This table prices the panel sizes and spacings already shown above, adding the one figure not yet covered there: installed cost.
Tighter spacing means more bars, more steel, and a higher price, at a fixed bar diameter. Widening the gap between bars is the most direct way to bring the cost down on any panel.
Take a 20×20 ft panel: going from 12 in to 18 in spacing cuts the bar count from 42 to 28 and drops the price by about 23%. That change also cuts the steel weight by about 33%, from 561 lb down to 374 lb.
At that tighter spacing, material's share runs about 32%, or $0.61 to $1.21 per lb for the steel itself, before setup and labor are added. Setup and labor split most of what remains.
The material rate is a calibrated blend of public $/lb and $/ft rebar prices, converted to pounds through the standard weight table this site uses elsewhere. All three cost lines grow together as spacing tightens, since more bars mean more steel and more time to place and tie them.
These figures add the same three parts every job page on this site prices: a flat setup fee, material, and labor to place and tie the bars. The labor rate behind this estimate leans on a single source, thinner proof than most of this site's other labor rates rest on.
Panel size matters on its own too. Still at that tighter spacing, the 24×24 ft panel covers 5.8 times as much ground as the 10×10 ft panel, yet costs only about 2.6 times as much. That flat fee weighs more heavily on the smaller panel.
Bar size matters too, apart from spacing. Swapping in a #5 bar for that 20×20 ft run adds about 56% more steel weight and raises the price by about 18%, with the number of bars and total length unchanged.
Installed cost also works out to a price per linear foot, which runs $1.27 to $2.51 for that same panel and spacing. That figure folds in the flat fee, so it runs higher on a short run than on a long one.
| Panel | Spacing | Total |
|---|---|---|
| 10×10 | 12 in | $525 – $1,040 |
| 10×10 | 16 in | $473 – $941 |
| 10×10 | 18 in | $456 – $907 |
| 20×20 | 12 in | $1,060 – $2,110 |
| 20×20 | 16 in | $889 – $1,770 |
| 20×20 | 18 in | $820 – $1,630 |
| 24×24 | 12 in | $1,370 – $2,730 |
| 24×24 | 16 in | $1,130 – $2,240 |
| 24×24 | 18 in | $1,040 – $2,070 |
Worked example: rebar for a 20×20 ft slab in the Boston, MA area
This is our estimate for #4 rebar on a 20×20 ft slab, spaced 12 in apart, in the Boston, MA area. A contractor's written quote can come in above or below it.
Rebar material is priced at a flat national rate, so only the labor rate changes with location; the range width also follows the local wage spread, since it applies everywhere. Cement mason wages here run about 24% above the national average.
Both ends differ from the national $1,060 to $2,110: the low end is about 10% higher and the high end about 9% higher. This range is narrower than the national one because local cement mason wages have a tighter spread than wages nationwide, per BLS OEWS wage percentiles.
Switch the location above to price this for your own area.
| Line item | Amount |
|---|---|
| Mobilization (site setup & delivery) | $340 – $660 |
| #4 rebar material | $340 – $680 |
| Labor & placement | $490 – $950 |
| Total | $1,170 – $2,290 |
How this estimate is calculated
Quantity (bars, length, and weight) is calculated directly from standard ASTM A615 rebar sizing. This concrete slab rebar calculator also shows a separate installed cost estimate, clearly flagged as lower confidence, since public data for installed rebar pricing comes from a single source.
Rebar calculator questions
How much rebar do I need for a slab?
A 20×20 ft slab with a two-way #4 grid at 12 in spacing needs 42 bars, for 840 lin ft of rebar total. At the standard ASTM A615 weight for a #4 bar, that run weighs about 561 lb. Wider spacing lowers both the bar count and the weight.