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Length imperial. Weight lb. Currency USD. Weight uses 1 lb = 0.45359237 kg. Currency converts US-dollar planning prices and does not change volumes, counts, or geometry.

20×30 Slab at 6 Inches: Rebar, Bags, and Truck

A 20 by 30 ft pad at 6 in, with the thickness table repeating the takeoff at the other standard depths.

Formula SSC-2026.1

Formula SSC-2026.1 · 4,000 PSI

Order volume

12.22 yd³

9.345 m³ placed+waste

Order weight

49,500 lb

22,453 kg

80 lb bags

550

14 pallets at 42 bags

60 lb bags

734

0.45 ft³ yield each

Rebar

840.00 ft

49 × 20 ft · 70 × 6 m · 617 lb

Ready-mix vs bags

$2,016.67

Truck $2,016.67 · 80 lb bags $3,712.50

Slab footprint and rebar gridLive scaled blueprint
20.00 ft30.00 ft#4 / 12 mm at 18 in OC · 6 in slab

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.

Bill of materials and shopping list
ItemNetWasteOrderUnit priceLine total
Ready-mix concrete11.11 yd³10%12.22 yd³ / 9.345 m³USD$2,016.67
Short-load feeFull load—2 truck @ 10 yd³USD$0.00
80 lb pre-mix bags500.0 bags10%550 bagsUSD$3,712.50
60 lb pre-mix bags666.7 bags10%734 bagsUSD$3,963.60
#4 rebar sticks, 20 ft49 sticks10%54 sticks / 70 × 6 mUSD$756.00
Rebar chairs294 crossings10%324 chairsUSD$90.72
Tie wire rolls294 ties10%2 rollsUSD$16.00

Ready-mix truck

$2,016.67

1.22 nominal 10 yd³ loads · 2 to order

80 lb bags

$3,712.50

60 lb alternative $3,963.60 · delivery weight 49,500 lb

Side-by-side thickness comparison at the same footprint
ThicknessOrder yd³Order m³80 lb bagsRebar ftReady-mix80 lb cost
4 in8.156.230367924$1,344.44$2,477.25
5 in10.197.787459924$1,680.56$3,098.25
6 in12.229.345550924$2,016.67$3,712.50
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: 20×30 Slab at 6 Inches: Rebar, Bags, and Truck

Prepared by

Date

Verified by (PE / electrician / inspector)

License number

Signature

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

A 20 by 30 ft rectangle at 6 in is about 11.11 cubic yards before waste. This page adds 10 percent waste, prices 4,000 PSI ready-mix against 80 lb and 60 lb bags, and lays #4 bar at 18 in on center. The comparison table repeats the same footprint at 4, 5, and 6 in so the extra inch of thickness is only extra volume, not a different grid. Soil bearing, vapor retarder, and joints are not designed here.

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 cubic yards is a 20 by 30 slab at 6 in before waste?
Length times width times thickness in feet, divided by 27, is about 11.11 cubic yards. The order line then applies the waste factor on the page.
Does the rebar count change when the slab gets thicker?
No. The grid follows the length, width, and spacing. Thickness changes volume, weight, bags, and the ready-mix price.
When is a truck cheaper than bags?
Compare the ready-mix line, including any short-load fee under 4 yards, with the 80 lb bag line. Both use the prices typed on the page.

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