Concrete Calculator for a Slab
Estimate cubic yards and bags of concrete for any slab pour.
Concrete volume is length × width × thickness. Convert thickness from inches to feet by dividing by 12, then divide the resulting cubic feet by 27 to get cubic yards.
Cubic yards
1.23
33.33 ft³ · 0.94 m³
60 lb bags
73
Quikrete or similar
80 lb bags
57
Quikrete or similar
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Recommended tools & materials
Handy picks for this project on Amazon.
Quikrete Concrete Mix (80 lb)
Standard high-strength bagged mix
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Concrete Mixing Tub
Mix bags by hand without a mixer
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Magnesium Bull Float
Smooth and level fresh slabs
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Concrete Edger & Groover Set
Clean edges and control joints
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How does the concrete calculator work?
Concrete volume is length × width × thickness. Convert thickness from inches to feet by dividing by 12, then divide the resulting cubic feet by 27 to get cubic yards.
Formula: yd³ = (L ft × W ft × T in ÷ 12) ÷ 27
A 60 lb bag of pre-mix yields about 0.017 yd³ (0.45 ft³); an 80 lb bag yields about 0.022 yd³ (0.60 ft³). Ready-mix trucks typically start at 1 yd³ minimum.
What else do people ask about this calculator?
How thick should a concrete slab be?
For a shed floor, patio or walkway, 4 inches of concrete is standard. Driveways, garage floors and slabs supporting heavy equipment should be 5–6 inches thick. Always pour over a compacted gravel base at least 4 inches deep.
How many bags of concrete for a 10x10 slab?
A 10×10 ft slab at 4 in thick is about 1.24 cubic yards, or roughly 84 bags of 60 lb concrete mix (56 bags of 80 lb). For anything over 1 cubic yard, ready-mix delivery is usually cheaper than bagged concrete.
Should I order extra concrete for a slab?
Yes — order 5–10% more than your calculated volume to account for uneven subgrade, spillage and formwork variance. Running short mid-pour causes a cold joint and weakens the slab.
How much concrete do I need for a 10×10 slab?
A 10×10 ft slab at 4 in thick needs about 1.23 cubic yards (33 ft³) — roughly 56 bags of 80 lb pre-mix or 74 bags of 60 lb pre-mix.
How thick should a concrete slab be?
A 4 in slab is standard for patios and walkways. Driveways use 4–6 in, and garage floors usually 4 in over compacted base.
How many 80 lb bags of concrete in a yard?
About 45 bags of 80 lb pre-mix make one cubic yard. For 60 lb bags, it takes about 60 bags per yard.
Should I add waste to my concrete estimate?
Yes — add 5–10% to account for spillage and uneven subgrade. This calculator returns the raw volume; round up when ordering.
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