How many cubic feet are in an 80 lb bag?

Roughly 0.6 cubic feet per 80 lb bag. We use that to estimate bag counts.

What if I’m using 60 lb bags?

Multiply the 80 lb bag estimate by about 1.33 to convert to 60 lb bags.

What waste percentage should I pick?

5–10% is common. Increase it for rough trenches, hand mixing, or when access is difficult.

Does this handle pier footings or pads?

This is for continuous strip footings. For pads or piers, calculate each volume separately.

Does this include rebar requirements?

No. Reinforcement, frost depth, and soil bearing need to follow local code or an engineer’s design.

construction calculator

Concrete Footing Calculator

Estimate footing volume and 80 lb bags from length, width, and depth.

Results

Volume (cubic ft): 44.00
Volume (cubic yd): 1.63
80 lb bags (approx): 73.33

How to use this calculator

Enter footing length and width in feet and depth in inches.
Choose a waste allowance to cover spillage and over-excavation.
Review cubic feet, cubic yards, and approximate 80 lb bag counts.

Inputs explained

Footing length: Total linear length of the footing run in feet.
Footing width: Footing thickness/width in feet.
Depth: Footing depth in inches. We convert to feet for volume.
Waste allowance: Extra percentage to cover overdig, spillage, and uneven subgrade.

How it works

Volume = length × width × depth (converted to feet).

Waste factor adds a buffer to the cubic feet before converting to yards and bag counts.

Formula

Volume ft³ = L × W × (Depth ÷ 12)
Bags ≈ Volume ÷ 0.6

When to use it

Ordering ready-mix concrete for foundation footings.
Estimating DIY bag counts for small runs or additions.
Budgeting concrete quantities before excavation.

Tips & cautions

Common waste factors range from 5–10% depending on trench quality and crew experience.
Round up to the next truck load or pallet of bags to avoid short loads.
If using 60 lb bags, multiply the 80 lb bag count by about 1.33.
Assumes a rectangular footing cross-section with consistent width and depth.
Does not include reinforcement, frost depth, or soil bearing considerations.
Large pours may require different waste factors based on pump/placement method.

Worked examples

20 ft × 2 ft × 12 in, 10% waste

Volume ≈ 44 ft³
Yards ≈ 1.63
Bags ≈ 73

12 ft × 1.5 ft × 18 in, 5% waste

Volume ≈ 27 ft³
Yards ≈ 1.0
Bags ≈ 45

Deep dive

This concrete footing calculator estimates cubic yards and 80 lb bag counts from footing length, width, depth, and waste factor. Enter your dimensions to size a footing pour before calling the batch plant.

Use it to budget small foundation runs or DIY projects. Adjust the waste percentage for trench quality and round up to avoid short loads. Reinforcement and code requirements should be handled separately.

FAQs

How many cubic feet are in an 80 lb bag?: Roughly 0.6 cubic feet per 80 lb bag. We use that to estimate bag counts.
What if I’m using 60 lb bags?: Multiply the 80 lb bag estimate by about 1.33 to convert to 60 lb bags.
What waste percentage should I pick?: 5–10% is common. Increase it for rough trenches, hand mixing, or when access is difficult.
Does this handle pier footings or pads?: This is for continuous strip footings. For pads or piers, calculate each volume separately.
Does this include rebar requirements?: No. Reinforcement, frost depth, and soil bearing need to follow local code or an engineer’s design.

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