How much concrete do I need for a 10×10 slab?

For a 10′ × 10′ slab at 4″ thick with a 10% waste margin: 1.36 cubic yards (62 × 80lb bags or 82 × 60lb bags). Without the waste margin, the raw volume is 1.23 cubic yards (56 × 80lb / 75 × 60lb). Use the Slab mode below to compute your exact dimensions in imperial or metric. Metric: For a 3 m × 3 m slab at 100 mm thick with a 10% waste margin: 0.990 m³, about 85 × 25kg bags or 106 × 20kg bags. Without the waste margin, the raw volume is 0.900 m³.

Why does the calculator add a waste margin?

Concrete losses (spillage, over-trowel, formwork imperfections) typically run 5–15%. A 10% margin is the construction-industry default. If your forms are tight you can drop it to 5%; if conditions are difficult, bump to 15%.

How many cubic feet are in a cubic yard?

Exactly 27. A cubic yard is 3 × 3 × 3 feet. In metric, 1 cubic yard ≈ 0.7646 m³. Metric: Exactly 1000 litres are in 1 cubic meter. A 3 m × 3 m slab at 100 mm thick is 0.900 m³, or 900 litres of concrete before waste.

How many 80lb bags of concrete are in a cubic yard?

About 45. Each 80lb bag yields 0.60 ft³, so 27 ÷ 0.60 = 45 bags per cubic yard. Metric: About 86. Each 25kg bag yields about 11.7 litres (0.0117 m³), so 1 ÷ 0.0117 ≈ 86 bags per m³.

How much concrete does a 25kg bag yield?

About 11.7 litres (0.0117 m³). A 20kg bag yields about 9.4 litres. So 1 m³ of concrete needs roughly 86 × 25kg bags or 107 × 20kg bags.

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Concrete Calculator

Estimate how much ready-mix concrete or how many bags you'll need for a slab or cylindrical footing. Live cubic yards, cubic feet, and bag counts. Imperial or metric, auto-detected by region, with a 10% waste margin built in.

Units

Slab Dimensions

Length (ft)

Width (ft)

Thickness (in)

Waste margin (%)

Slab visual 4 in thick · 10% waste

Use the thickness chips and waste slider together: thicker pads and higher waste visibly grow the order before bags are rounded up.

Total Volume - Cubic Yards - ft³ · includes waste

80lb Bags -

60lb Bags -

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Need bag counts?

Use the concrete bag calculator guide for quick 80lb, 60lb, 25kg, and 20kg bag estimates before you order. Estimating a continuous footing? Use the concrete footing calculator for footing volume, bags, waste, and rough concrete cost. Setting fence or deck posts? Open the post hole concrete calculator for diameter, depth, post subtraction, and bag yield. Need a rough total? Try the concrete slab cost calculator for concrete, base prep, forms, and labor. Planning demo or hauling? Check the concrete weight calculator for pounds, tons, kilograms, and metric tonnes from the same dimensions. Building a stone base first? Use the gravel calculator for crushed stone yards, tons, compaction allowance, and material cost. Filling a trench or utility over-excavation with CLSM? Use the flowable fill calculator for trench volume, truck allowance, waste, and rough material cost. Reinforcing the pour? Use the rebar calculator for slab-grid bars, stock sticks, steel weight, and material cost.

How to use this calculator

Measure the length, width, and thickness of the area you're pouring. For slabs and patios, thickness is usually 4″. For footings, plan on 8-12″. For driveways and load bearing applications, plan on 6″ or more. The calculator returns volume in cubic yards (imperial) or m³ (metric) plus the equivalent number of pre-mixed bags. We add 10% waste by default because real pours always need a little extra.

The formula

Volume (cubic feet) = length × width × thickness, with thickness converted to feet. Divide by 27 for cubic yards.

Worked example. A 10′ × 10′ slab at 4″ thick:

Volume: 10 × 10 × (4 ÷ 12) = 33.33 ft³
Cubic yards: 33.33 ÷ 27 = 1.23 yd³
80lb bags (each yields 0.60 ft³): 33.33 ÷ 0.60 ≈ 56 bags
60lb bags (each yields 0.45 ft³): 33.33 ÷ 0.45 ≈ 75 bags

Add 5-15% waste margin (10% default) for spillage, over-trowel, and formwork imperfections.

Bag yield reference

Bag size	Yield	Per cubic yard / m³
60 lb	0.45 ft³	60 per yd³
80 lb	0.60 ft³	45 per yd³
20 kg	9.4 L (0.0094 m³)	107 per m³
25 kg	11.7 L (0.0117 m³)	86 per m³

Common slab sizes (raw volume, no waste)

Slab	at 4″at 100 mm	at 6″at 150 mm
8′ × 8′2.4 m × 2.4 m	0.79 yd³0.576 m³	1.19 yd³0.864 m³
10′ × 10′3 m × 3 m	1.23 yd³0.900 m³	1.85 yd³1.350 m³
12′ × 12′3.6 m × 3.6 m	1.78 yd³1.296 m³	2.67 yd³1.944 m³
16′ × 16′4.8 m × 4.8 m	3.16 yd³2.304 m³	4.74 yd³3.456 m³
20′ × 20′6 m × 6 m	4.94 yd³3.600 m³	7.41 yd³5.400 m³
24′ × 24′7.2 m × 7.2 m	7.11 yd³5.184 m³	10.67 yd³7.776 m³

Above ≈1.5 cubic yards (≈12′ × 12′ at 4″) ready-mix delivery is usually cheaper and faster than bagged. Above 3 yards, almost always. Above about 1.1 m³, ready-mix delivery is usually cheaper and faster than bagged concrete. Above 2.3 m³, almost always.

Common Questions

How much concrete do I need for a 10×10 slab?How much concrete do I need for a 3 m × 3 m slab?: For a 10′ × 10′ slab at 4″ thick with a 10% waste margin: 1.36 cubic yards (62 × 80lb bags or 82 × 60lb bags). Without the waste margin, the raw volume is 1.23 cubic yards (56 × 80lb / 75 × 60lb). Use the Slab mode below to compute your exact dimensions in imperial or metric.For a 3 m × 3 m slab at 100 mm thick with a 10% waste margin: 0.990 m³, about 85 × 25kg bags or 106 × 20kg bags. Without the waste margin, the raw volume is 0.900 m³.
Why does the calculator add a waste margin?Why does the calculator add a waste margin?: Concrete losses (spillage, over-trowel, formwork imperfections) typically run 5–15%. A 10% margin is the construction-industry default. If your forms are tight you can drop it to 5%; if conditions are difficult, bump to 15%.Concrete losses (spillage, over-trowel, formwork imperfections) typically run 5–15%. A 10% margin is the construction-industry default. If your forms are tight you can drop it to 5%; if conditions are difficult, bump to 15%.
How many cubic feet are in a cubic yard?How many litres are in a cubic meter?: Exactly 27. A cubic yard is 3 × 3 × 3 feet. In metric, 1 cubic yard ≈ 0.7646 m³.Exactly 1000 litres are in 1 cubic meter. A 3 m × 3 m slab at 100 mm thick is 0.900 m³, or 900 litres of concrete before waste.

How many 80lb bags of concrete are in a cubic yard?How many 25kg bags of concrete are in a cubic meter?: About 45. Each 80lb bag yields 0.60 ft³, so 27 ÷ 0.60 = 45 bags per cubic yard.About 86. Each 25kg bag yields about 11.7 litres (0.0117 m³), so 1 ÷ 0.0117 ≈ 86 bags per m³.
How much concrete does a 25kg bag yield?How much concrete does a 25kg bag yield?: About 11.7 litres (0.0117 m³). A 20kg bag yields about 9.4 litres. So 1 m³ of concrete needs roughly 86 × 25kg bags or 107 × 20kg bags.About 11.7 litres (0.0117 m³). A 20kg bag yields about 9.4 litres. So 1 m³ of concrete needs roughly 86 × 25kg bags or 107 × 20kg bags.

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