30×40 Barn Slab at 6 Inches and 4,000 PSI
A 30 by 40 ft agricultural slab at 6 in with a 16 by 12 in turned-down edge.
Formula SSC-2026.1
Formula SSC-2026.1 · 4,000 PSI
Order volume
28.10 yd³
21.486 m³ placed+waste
Order weight
113,813 lb
51,625 kg
80 lb bags
1,265
31 pallets at 42 bags
60 lb bags
1,687
0.45 ft³ yield each
Rebar
1,930.00 ft
110 × 20 ft · 133 × 6 m · 1,418 lb
Ready-mix vs bags
$4,636.84
Truck $4,636.84 · 80 lb bags $8,538.75
Grid lines are equalized so the drawing stays readable. The order count uses on-center spacing with a bar at each end of the layout, then holds concrete cover in the field.
| Item | Net | Waste | Order | Unit price | Line total |
|---|---|---|---|---|---|
| Ready-mix concrete | 25.55 yd³ | 10% | 28.10 yd³ / 21.486 m³ | USD | $4,636.84 |
| Short-load fee | Full load | — | 3 truck @ 10 yd³ | USD | $0.00 |
| 80 lb pre-mix bags | 1,149.6 bags | 10% | 1,265 bags | USD | $8,538.75 |
| 60 lb pre-mix bags | 1,532.8 bags | 10% | 1,687 bags | USD | $9,109.80 |
| #4 rebar sticks, 20 ft | 110 sticks | 10% | 121 sticks / 133 × 6 m | USD | $1,694.00 |
| Rebar chairs | 567 crossings | 10% | 624 chairs | USD | $174.72 |
| Tie wire rolls | 567 ties | 10% | 3 rolls | USD | $24.00 |
Ready-mix truck
$4,636.84
2.81 nominal 10 yd³ loads · 3 to order
80 lb bags
$8,538.75
60 lb alternative $9,109.80 · delivery weight 113,813 lb
| Thickness | Order yd³ | Order m³ | 80 lb bags | Rebar ft | Ready-mix | 80 lb cost |
|---|---|---|---|---|---|---|
| 5 in | 24.64 | 18.837 | 1,109 | 2,123 | $4,065.20 | $7,485.75 |
| 6 in | 28.10 | 21.486 | 1,265 | 2,123 | $4,636.84 | $8,538.75 |
| 8 in | 35.03 | 26.783 | 1,577 | 2,123 | $5,780.12 | $10,644.75 |
Show the deterministic formula
Slab ft³ = L × W × thickness ÷ 12. Thickened-edge extra = footing band × (footing depth − slab thickness), with corner squares counted once.
yd³ = ft³ ÷ 27. m³ = ft³ × 0.0283168. Weight uses 150 lb/ft³, then the header converts that pound total at 1 lb = 0.45359237 kg. 80 lb bags yield 0.6 ft³ and 60 lb bags yield 0.45 ft³. Currency changes the price labels only.
Bars across a span = floor(span ÷ spacing) + 1. Order sticks = that count, plus 10, 5, or 15 percent waste, cut from 20 ft and 6 m stock. Chairs = one per grid intersection.
Contractor sign-off
Project: 30×40 Barn Slab at 6 Inches and 4,000 PSI
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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.
Engineering notes
Thirty by forty feet at 6 in is 22.22 cubic yards before waste. The thickened edge is 16 in wide and 12 in deep, so the extra concrete is only the 6 in below the slab. At 10 percent waste this is more than two nominal 10 yard trucks. Specify 4,000 PSI on the order ticket to match the price you type in. Hay, equipment, and point loads still need a design if the barn is permitted.
Code reference
IRC R506.1 sets a 3.5 in minimum for concrete slab-on-ground floors. Reinforcement cover and spacing follow ACI 318 practice and the local inspector. This quantity takeoff is not a soils or structural design.
Field questions
- How many trucks for a 30x40 by 6 inch slab?
- Start from the order yards, including the edge and waste, and divide by 10. The result card rounds up to whole trucks.
- Does 4,000 PSI change the volume?
- No. PSI changes the specification and the price you enter. Volume depends on thickness, area, and the thickened edge.
- What rebar spacing is preset?
- #4 bars at 18 in on center, plus two continuous edge bars because the turn-down is on.