How Much Concrete for a 4x4 Slab?

A 4 × 4 ft slab (16 ft²) poured 4 inches thick needs 0.20 cubic yards of concrete, which is 9 bags of 80 lb mix. Allow 10% for waste and order 0.22 yd³ (10 bags). Change the thickness below for a 5 or 6 inch slab.

Results

Concrete needed

0.22 cubic yards

Includes your waste allowance

Cubic feet: 5.9 ft³
Cubic meters: 0.17 m³
Estimated weight: 880 lb

If you mix bagged concrete

80 lb bags: 10 bags
60 lb bags: 14 bags
40 lb bags: 20 bags

Bag yields used: 0.60 ft³ per 80 lb, 0.45 ft³ per 60 lb, 0.30 ft³ per 40 lb. Check your bag, since brands differ slightly.
Ready-mix is usually ordered in ¼ yard steps. Round up rather than down.

Concrete needed for a 4 × 4 ft slab, by thickness

These figures are for the whole 16 ft² slab. The last column adds 10% for waste, which is what we suggest you order.

Thickness	Cubic feet	Cubic yards	80 lb bags	60 lb bags	Yards with 10% waste
4 in	5.3	0.20	9	12	0.22
5 in	6.7	0.25	12	15	0.27
6 in	8.0	0.30	14	18	0.33
8 in	10.7	0.40	18	24	0.43

What a 4 × 4 slab is used for

A 4 × 4 ft slab is a small pad: typical for an air conditioner or heat pump condenser, a generator, a storage box, a bench, or a landing outside a door. Four inches is plenty for these light loads.

Bags or ready-mix for 4 × 4 ft?

At 0.22 cubic yards, bagged concrete is the sensible choice. You will mix about 10 bags of 80 lb, which is manageable in a wheelbarrow or a small mixer, and no truck is needed.

Don't forget what goes under and inside it

A slab needs a compacted base, usually 4 inches of gravel, which for this size is about 0.24 cubic yards after allowing for compaction (see the gravel calculator). Reinforcement such as rebar or wire mesh holds cracks tight: the rebar calculator counts bars for a 4 × 4 ft grid.

Want to change anything else? The calculator above is the full Concrete Calculator: edit any number and the results update instantly.

Tools & materials for this project

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80 lb concrete mixFor small slabs and repairs Concrete mixerSaves your back past 10 bags Concrete finishing toolsFloat, edger and groover Wire mesh reinforcementControls shrinkage cracks Form stakesHold your forms straight

Frequently asked questions

How many bags of concrete for a 4x4 slab?

For a 4 inch slab you need 9 bags of 80 lb concrete (12 bags of 60 lb), or 10 bags of 80 lb with 10% waste. For a 6 inch slab it is 14 bags of 80 lb, or 15 with 10% waste.

How many cubic yards is a 4x4 slab?

A 4 × 4 ft slab is 0.20 yd³ at 4 inches, 0.25 yd³ at 5 inches and 0.30 yd³ at 6 inches, before waste. Add 5 to 10% when you order.

How much does a 4x4 concrete slab weigh?

At 4 inches thick it weighs roughly 800 lb (0.4 tons), at about 150 lb per cubic foot. At 6 inches it is about 1,200 lb.

Related sizes and guides

Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.

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