Calculators / Concrete

Concrete Calculator: Bags, Volume & Gravel Base for a Slab

Size the pour. Leave with a batch ticket.Bags, net volume, compacted base, form boards and control joints.

PopularDeckConcreteFence
Pour ticket10 ft × 12 ft · 4 in slab
Concrete to buy
67
80 lb bags1.48 cu yd · 40.0 cu ft net
10 ft12 ft4 in3 in base

5,360 lb on the truck67 × 80 lb, about 2 pallets

120 sq ftFootprint
30 cu ftGravel base
44 ftForm boards

Slab size

Concrete bag
More options: allowance, reinforcement

Ticket updates as you type

How it’s calculated

Volume = 10 ft × 12 ft × (4 in ÷ 12) = 40 cu ft

40 ÷ 27 = 1.48 cu yd

Bags = 40 cu ft ÷ 0.6 cu ft ≈ 66.7 → 67

Base = 120 sq ft × (3 in ÷ 12) = 30 cu ft

Net geometry, rounded up. Waste is only added through Extra allowance. Displayed measurements are rounded; calculations use full precision. Yields are the manufacturer’s published figures.

Material list

Material & specificationQuantity
Concrete mix80 lb bags · 0.6 cu ft yield67 bags
Compacted gravel base3 in compacted depth30 cu ft
Form boards2×4 or 2×6 lumber, selected to match slab depth44 ft
Control jointsGroove at least 1 in deep10 ft
ReinforcementMesh, rebar or fiber selection depends on the slab designConfirm
Stakes & form screwsSpacing depends on soil and form-board stiffnessConfirm
Cure-and-sealCoverage varies by selected product and surface finishConfirm
Price this slab
Warnings & assumptions

This takeoff covers a simple rectangular slab. Footings, thickened edges, steps, slopes and grade beams need separate geometry.

Confirm reinforcement, subgrade, drainage, load and local-code requirements before purchase.

Bag count is net geometric volume rounded up. Add an explicit allowance if excavation is uneven or spillage is likely.

Slab footprint: 10 × 12 ft (user)

Length and width set the form perimeter, base volume and concrete volume.

Slab thickness: 4 in (user)

The user-set thickness directly controls concrete volume.

QUIKRETE, Pouring & Finishing Concrete Slabs (https://www.quikrete.com/athome/video-pouring-concrete-slabs.asp)

Compacted base: 3 in (user)

QUIKRETE's slab guide calls for 3–4 in of compacted all-purpose gravel; the conservative low-volume default is 3 in.

QUIKRETE, Pouring & Finishing Concrete Slabs (https://www.quikrete.com/athome/video-pouring-concrete-slabs.asp)

Concrete package: 80 lb bags · 0.6 cu ft published yield (user)

Bag count is volume divided by the manufacturer's published yield, always rounded up.

QUIKRETE Concrete Mix #1101 data sheet (https://www.quikrete.com/pdfs/spec_data-concretemix.pdf)

Extra concrete allowance: 0% (user)

This allowance was explicitly set by the user.

Reinforcement: Confirm project-specific design (user)

Slab dimensions do not reveal traffic load, soil, exposure or local reinforcement requirements.

QUIKRETE, Pouring & Finishing Concrete Slabs (https://www.quikrete.com/athome/video-pouring-concrete-slabs.asp)

Purchase checklist & notes

  • 80 lb bags · 0.6 cu ft yield

    40 cu ft (1.48 cu yd) net slab volume.

  • Mesh, rebar or fiber selection depends on the slab design

    Confirm: Confirm reinforcement and support details for the actual load, soil, climate and local code.

  • 3 in compacted depth

    Convert to bags only after selecting a gravel product with a published bag volume.

  • 2×4 or 2×6 lumber, selected to match slab depth

    Net perimeter; choose stock lengths to keep joints supported.

  • Spacing depends on soil and form-board stiffness

    Confirm: Set the stake and screw schedule after the form lumber and site soil are known.

  • Groove at least 1 in deep

    Interior joint length keeping each direction at 10 ft or less.

  • Coverage varies by selected product and surface finish

    QUIKRETE specifies water curing or an appropriate cure-and-seal after finishing.

    Confirm: Choose the curing method/product, then apply its published coverage rate.

This takeoff covers a simple rectangular slab. Footings, thickened edges, steps, slopes and grade beams need separate geometry.

Confirm reinforcement, subgrade, drainage, load and local-code requirements before purchase.

Bag count is net geometric volume rounded up. Add an explicit allowance if excavation is uneven or spillage is likely.

Edit the project basis to save your calculation.

This takeoff covers a simple rectangular slab. Footings, thickened edges, steps, slopes and grade beams need separate geometry.

Confirm reinforcement, subgrade, drainage, load and local-code requirements before purchase.

Bag count is net geometric volume rounded up. Add an explicit allowance if excavation is uneven or spillage is likely.

How it’s calculated

Volume = 10 ft × 12 ft × (4 in ÷ 12) = 40 cu ft

40 ÷ 27 = 1.48 cu yd

Bags = 40 cu ft ÷ 0.6 cu ft ≈ 66.7 → 67

Base = 120 sq ft × (3 in ÷ 12) = 30 cu ft

Net geometry, rounded up. Waste is only added through Extra allowance. Displayed measurements are rounded; calculations use full precision. Yields are the manufacturer’s published figures.

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Cost estimates on pricetobuild

Deck costConcrete slab costFence costDriveway costRetaining wall costPaver patio cost

Bag count starts with published yield

A bag label is a weight, not a volume. This takeoff converts slab geometry to cubic feet, then uses the manufacturer’s published yield for the selected bag. That keeps the arithmetic auditable and the final partial bag rounded up. To compare bagged mix against an installed price, price the slab in the cost calculator. For round piers and footings, use the sonotube calculator; for fence posts, the fence post concrete calculator.

The base is part of the takeoff

The default compacted gravel depth is 3 in, the lower end of QUIKRETE’s 3–4 in slab-guide range. Gravel stays in cubic feet until a bag with a published volume is selected.

Structural choices stay open

A patio, driveway and equipment pad can share dimensions and require different reinforcement. The list names that missing decision instead of inventing a mesh or rebar schedule from geometry alone.

Questions before the pour

How many concrete bags do I need for a slab?

The calculator multiplies slab length, width and thickness for net volume, then divides by QUIKRETE's published yield: 0.60 cubic feet for an 80 lb bag or 0.45 cubic feet for a 60 lb bag. The final bag count always rounds up.

Does the calculator automatically add waste?

No. The cited manufacturer data does not prescribe one universal allowance, so the default is zero rather than a hidden guess. You can add an explicit percentage for uneven excavation or spillage.

Does this tell me what reinforcement to use?

No. Dimensions alone do not reveal loads, soil, exposure or local rules. Reinforcement stays marked for confirmation unless you explicitly choose a fiber-reinforced bagged mix.

Can I see the complete result without entering an email?

Yes. Concrete, base, forms, joints and finish items appear first. Sending or printing the list is optional and appears only after the complete result.