30x50 Concrete Slab, 4 Inches Thick
Poured 4 in thick, a 30 × 50 ft slab covering 1,500 sq ft needs about 20.37 cubic yards of concrete once 10% is added for waste. For ready-mix, order 20.5 cu yd for the 30x50, about $2,870 – $3,690 delivered. Bagged, the same 30x50 is 917 80 lb or 1,223 60 lb bags, about $6,115 – $8,561 for the concrete alone.
- Ready-mix order
- 20.5 cu yd
- Ready-mix cost
- $2,870 – $3,690
- 80 lb bags
- 917
- Bag cost
- $6,115 – $8,561
Materials only for a 30x50 at 4 in, from national price ranges as of 2026-09; not a live quote.
Using a 30x50 slab
A 30x50 holds a three-bay garage with a 20 ft shop at one end, or a pole barn for a camper, a boat and a tractor.
At 1,500 sq ft, this is a multi-truck pour; many contractors place it in two halves on separate days with a construction joint between them.
Long buildings like this get a run of control joints across the 50 ft length, so plan where they fall around the doors and the posts.
A 4 in 30x50 pour: check first
- Agree on one pour or two halves with the contractor, and where the construction joint goes.
- Mark post locations in a pole barn so the joints do not land right beside them.
- Schedule a pump if the trucks cannot reach the far side.
Full plan for a 30x50 slab, 4 in
- Area
- 1,500 sq ft
- Thickness
- 4 in
- Volume
- 20.37 cu yd
Bagged concrete estimate (DIY)
$7,568 – $10,926
Est. as of 2026-09 — not a live quote
Ready-mix delivered (materials only)
$2,870 – $3,690
Est. as of 2026-09 — not a live quote
For a pour this size, ready-mix delivery is typically more practical than mixing bags by hand.
Shopping list
- Concrete mix (60 lb bags) Or 1,834 × 40 lb, 1,467 × 50 lb or 917 × 80 lb bags. 1,223 bags
- Ready-mix concrete Alternative to bagged mix; most suppliers have a 1 cu yd order minimum. 20.5 cu yd
- Compactable gravel sub-base 4 in compacted base beneath the slab. 25 tons
- 6x6 welded wire mesh Reinforcement for crack control; not a substitute for engineered rebar on structural slabs. 1,650 sq ft
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Buy bagged concrete
Pick up bagged mix and reinforcement from a hardware store for smaller pours.
View shopping listAssumptions
- Waste allowance: 10% applied to account for over-excavation and spillage.
- Approx. wet weight: 82,500 lb (41.3 tons).
- Prices are national-average retail/delivery ranges as of 2026-09, not live quotes.
Bags or ready-mix for a 30x50 slab, 4 in?
The 30x50 at 4 in needs 3 trucks: 20.5 cu yd at 8 cu yd a load, the low end of what a truck carries, for about $2,870 – $3,690. Ask the supplier to space the trucks so each load goes down before the last one stiffens (a wet edge), line up enough hands to place and finish 1,500 sq ft at 4 in, and ask about a pump if the truck can't reach every corner of the 30x50. Ready-mix wins for this 30x50 by roughly $4,058 (range midpoints), and nobody has to mix 917 bags by hand.
Is 4 in thick enough for a 30x50 slab?
Many residential garage floors the size of this 30x50 are poured 4 in thick, which clears the IRC minimum of 3-1/2 in for cars and light trucks. Go to 5 or 6 in if the 30x50 will hold heavy pickups, an RV, a car lift or a tractor, or sits on soft or clay soil, and check your local code first. At 6 in the same 30x50 takes about 30.56 cu yd.
Control joints for a 30x50 slab at 4 in
Like any slab, a 4 in 30x50 shrinks while it cures; control joints decide where its cracks go. ACI and PCA guidance spaces joints 24 to 36 times the thickness, which for this 30x50 at 4 in is every 8 to 12 ft, sawn 1 in deep (a quarter of the slab) once the surface holds up to the blade, usually within a day.
On the 30x50 at 4 in, a joint every 10 ft or less means 4 joints across the 50 ft side and 2 joints across the 30 ft side: 15 panels of about 10 × 10 ft and 220 ft of saw cut. The 30x50 is 1.7 times as long as it is wide, and long, narrow slabs crack across their width, so don't skip its cross joints.
How much a 30x50 slab 4 in thick weighs
At roughly 150 lb per cubic foot of wet concrete, a 30x50 at 4 in puts about 82,500 lb (41.3 tons) on the ground. As bags, the 30x50 is 917 80 lb bags, 73,360 lb in all: about 49 trips in a pickup carrying 1,500 lb a load. Nobody hauls 73,360 lb of bags for a 30x50 in a pickup; it comes by ready-mix truck or as pallets on a delivery truck.
The 30x50 at 4 in against nearby sizes
Every row uses the same 10% waste and prices as the 30x50 at 4 in; costs are for the concrete only.
| Slab | Cu yd | 60 lb bags | 80 lb bags | Ready-mix order | Bags cost | Ready-mix cost |
|---|---|---|---|---|---|---|
| 30x40 slab, 4 in | 16.3 | 978 | 734 | 16.5 cu yd | $4,890 – $6,846 | $2,310 – $2,970 |
| 30x50 slab, 4 in (this page) | 20.37 | 1,223 | 917 | 20.5 cu yd | $6,115 – $8,561 | $2,870 – $3,690 |
| 40x40 slab, 4 in | 21.73 | 1,304 | 978 | 21.75 cu yd | $6,520 – $9,128 | $3,045 – $3,915 |
Questions about a 30x50 slab, 4 in
How many bags of concrete for a 30x50 slab 4 inches thick?
A 30x50 slab at 4 in takes about 917 80 lb bags or 1,223 60 lb bags (or 1,467 50 lb, 1,834 40 lb), with 10% added for waste: 550 cubic feet in all.
How many yards of concrete for a 30x50 slab 4 inches thick?
20.37 cubic yards with waste (18.52 without) for a 30x50 at 4 in. Round the 30x50 order to 20.5 cu yd: plants batch in quarter yards and most won't send less than a yard.
How much does a 30x50 concrete slab 4 inches thick cost?
Concrete alone for the 30x50 runs about $2,870 – $3,690 for 20.5 cu yd of ready-mix delivered, or $6,115 – $8,561 for 1,223 60 lb bags. Add a 4 in gravel base and wire mesh and the bagged 30x50 plan comes to $7,568 – $10,926. Labor, forms and finishing for a 30x50 at 4 in come on top of these national ranges (as of 2026-09), which are not quotes.
How much does a 30x50 concrete slab 4 inches thick weigh?
About 82,500 lb (41.3 tons) of wet concrete for the 30x50, at 150 lb per cubic foot. The 917 80 lb bags for a 30x50 weigh 73,360 lb: about 49 trips in a pickup carrying 1,500 lb a load.
Where do control joints go on a 30x50 slab 4 inches thick?
On a 30x50 at 4 in, every 8 to 12 ft (24 to 36 times the thickness), sawn 1 in deep. On the 30x50 at 4 in, a joint every 10 ft or less means 4 joints across the 50 ft side and 2 joints across the 30 ft side: 15 panels of about 10 × 10 ft and 220 ft of saw cut.
Limitations
The 30x50 figures at 4 in are material estimates and typical price ranges, not a quote or a structural design. Confirm that 4 in, the reinforcement and the joint layout suit your soil, loads and local code for a 30x50 slab with a qualified professional.