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Concrete Calculator (Slab, Yards & Bags)

How much concrete do I need for this slab — in cubic yards and bags?

Single calculationv1.0.0Verified 2026-11-01Runs in your browser

Spec sheet

slab_volume · v1.0.0

Method

Rectangular volume + waste

01V = length × width × thickness × (1 + waste)
021 yd³ = 27 ft³
03bags = V ÷ yield per bag (80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 40 lb ≈ 0.30 ft³)

Limits — read before relying on it

Rectangular shapes only.
Bag yields vary by product; ready-mix is usually cheaper above ~1 yd³.

Sources

Typical premix bag yields printed on U.S. concrete mix bagstextbook

Worked example

computed by the same formula

10 × 10 ft slab, 4 in

Inputs

Length: 10 ft
Width: 10 ft
Thickness: 4 in
Number of identical pours: 1
Waste / spillage allowance: 10 %

Result

Concrete: 1.36 yd³
Concrete: 1.04 m³
Concrete: 36.7 ft³
80 lb bags: 62
60 lb bags: 82
40 lb bags: 123

Questions

How is the concrete calculator calculated?

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Rectangular volume + waste. V = length × width × thickness × (1 + waste) · 1 yd³ = 27 ft³ · bags = V ÷ yield per bag (80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 40 lb ≈ 0.30 ft³)

Example: 10 × 10 ft slab, 4 in?

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Concrete: 1.36 yd³; concrete: 1.04 m³.

What does this calculator not cover?

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Rectangular shapes only. Bag yields vary by product; ready-mix is usually cheaper above ~1 yd³.

Where do the numbers come from?

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Sources: Typical premix bag yields printed on U.S. concrete mix bags. The formula is versioned (slab_volume v1.0.0) and covered by automated tests.

Is my data stored?

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No. The calculation runs in your browser and nothing is sent unless you choose to save a shareable link.

Also searched asconcrete calculator · how much concrete do i need · cubic yards of concrete · concrete bags calculator · slab concrete calculator

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