Rebar runs $0.50 to $1.00 per pound from suppliers, quoted as $1,300 to $2,000 per ton. At retail it's steeper — a 20-foot #4 stick at Home Depot runs $14.33, which works out to about $1.07 a pound. The good news for homeowners: most residential slabs need somewhere between 100 and 600 pounds of steel, so the whole package lands between $87 and $900. Here's how to get from your slab dimensions to a real number.
Steel is a commodity, and its price moves with the market, but the supplier bands are stable enough to plan around: $0.50 to $1.00 per pound, or $1,300 to $2,000 per US ton (2,000 lb). Those are the same number — divide the ton price by 2,000 and you get $0.65 to $1.00 per pound, right in the band.
Retail sits above supplier pricing because you're buying ones and twos. That $14.33 #4 stick from the box store is 13.4 lb of steel at $1.07 per pound; buy 50 or more and the price drops to $12.18, or about $0.91 per pound. A real supplier with a bulk order beats both, but small jobs often can't hit mill minimums, and that's fine — the premium on a $250 order is a pizza.
Bar size is eighths of an inch: #3 is ⅜ inch diameter, #4 is ½ inch. Each size has an ASTM A615 unit weight, and the stick price follows directly from it:
| Bar size | Weight per 20-ft stick | Box-store price (20 ft) | At $0.85/lb |
|---|---|---|---|
| #3 (⅜ in) | 7.5 lb | $5.38 | $6.39 |
| #4 (½ in) | 13.4 lb | $14.33 ($12.18 at 50+) | $11.36 |
| #5 (⅝ in) | 20.9 lb | $18-$22 | $17.73 |
| #6 (¾ in) | 30.0 lb | $25-$32 | $25.53 |
The #3 and #4 rows are shelf prices; #5 and #6 are computed from the per-pound bands since big-box stocking varies by region. Notice the crossover: at supplier pricing the heavier bars cost almost exactly their weight, but at retail the small bars are comparatively cheap and the big ones carry a real premium. Another box-store quirk: sticks longer than 8 feet often trigger a delivery surcharge, so a truck rental or a supplier will-call can be the smarter move on a two-stick-over order.
The count is grid math. Bars per direction = floor(length ÷ spacing) + 1, because a bar sits at each end. Total linear feet = (bars × width) + (bars × length), then add laps — 2 feet per stick is a working allowance — before dividing by 20 for stick count. Run it on the common cases with a 3-inch edge clearance:
| Slab | Bar & spacing | Bars | Length incl. laps | 20-ft sticks | Weight | Cost @ $0.85/lb |
|---|---|---|---|---|---|---|
| 10 × 10 ft (shed floor) | #4 @ 18 in | 14 | 154 lf | 8 | 103 lb | $87 |
| 20 × 20 ft (patio) | #4 @ 24 in | 20 | 440 lf | 22 | 294 lb | $250 |
| 24 × 24 ft (two-car) | #4 @ 18 in | 32 | 846 lf | 43 | 565 lb | $480 |
| 30 × 30 ft (drive/barn) | #5 @ 24 in | 30 | 990 lf | 50 | 1,033 lb | $878 |
Two habits keep these numbers honest. Spacing is measured on center, and it's set by your engineer or code, not by preference — light residential slabs typically run #3 or #4 at 12 to 18 inches on center per CRSI and ACI 318 guidance. And the bars need to sit in the lower third of the slab on chairs; steel lying on the ground does essentially nothing, because it never goes into tension where the design put it.
All three, which is why quotes for identical steel can look 30 percent apart. Box stores price per stick, usually bundled in tens. Suppliers price by weight — per pound or per ton — which makes their quotes comparable no matter how the bars get cut. On a big job, a fabricator cuts and bends to your bar schedule, and the quote goes by the ton plus a fabrication charge per bend.
Converting is just the unit weights. Twenty sticks of #4 is 267 lb, about 0.13 tons — below what anyone would call a mill order. A 30×30 driveway at half a ton starts to be worth a supplier phone call. And since quotes travel by weight, takeoffs should produce pounds, not just stick counts; that's how you'll be comparing apples when the invoices arrive.
Bar count, grid layout, sticks with laps, weight in pounds, tie wire, and cost from your slab dimensions and spacing.
Rebar Calculator →Price steel at $0.50-$1.00 per pound from a supplier, expect $5.38 to $14.33 per 20-foot stick at retail for #3 and #4, and let the slab size set the total — $87 for a shed floor, $250 for a 20×20 patio, around $480 for a two-car slab. Get pounds before you shop: the rebar calculator turns your dimensions and spacing into sticks, weight, and cost with the laps included. The concrete itself is the bigger line item, so run the concrete calculator for yardage at the same time, and if footings are part of the build, the sonotube calculator sizes those columns. Pouring a shed slab? Our shed cost guide walks the whole foundation sequence.
Suppliers run $0.50-$1.00 per pound, quoted as $1,300-$2,000 per ton. Retail is higher: a $14.33 twenty-foot #4 stick at a big box store works out to about $1.07 per pound, dropping to $0.91 at the 50-plus bundle price.
With #4 bar at 18 inches on center each way, a 10×10 slab takes 7 bars per direction — 14 total, 140 linear feet. That is 7 twenty-foot sticks, 8 once you add 2-foot laps, about 103 lb and $87 of steel at $0.85 per lb.
At #4 bar on 24 inch centers, a 20×20 slab needs 10 bars each way — 400 linear feet, or 440 feet including 2-foot laps, which is 22 twenty-foot sticks, 294 lb, and about $250 of steel at $0.85 per lb.
Tension lap splices run 30-40 times the bar diameter depending on concrete strength and conditions — roughly 12-20 inches for #4. ACI 318 tables give exact values; for small bars on residential work, overlapping at least 24 inches is the common safe default.
CRSI and ACI 318 guidance puts light residential slabs at #3 or #4 on 12-18 inch centers. #3 saves a little money on a 4-inch walkway or shed floor; #4 is the usual call for driveways and anything vehicular, and the price gap is small — about $5 per stick retail.