Worked example
How Many 80 lb Bags of Concrete for a 10x10 Slab?
This example uses the 80 lb bag yield preset for a 10 ft by 10 ft slab, then lets you change thickness or bag yield.
Quick answer
59 80 lb bags are needed for the default 10x10 slab: 4 in thick, 5% waste, and a 0.60 cu ft yield per bag. That equals 35.00 cu ft, about 1.30 cu yd after waste. Switching to 60 lb or 40 lb bags raises the count to 78 or 117 bags.
Calculator inputs
Concrete Slab Calculator Results
Results update in your browser as you edit inputs. They are planning estimates, not complete shopping lists.
Enter project dimensions to calculate material quantity.
Same 10x10 slab with 40, 60, or 80 lb bags
All rows use the example defaults: a 10 ft by 10 ft slab, 4 in thick, with 5% waste. Bag counts are rounded up from the calculator output.
| Bag size | Preset yield | Bags needed |
|---|---|---|
| 40 lb bag | 0.30 cu ft | 117 bags |
| 60 lb bag | 0.45 cu ft | 78 bags |
| 80 lb bag | 0.60 cu ft | 59 bags |
Preset yields are planning approximations. Confirm the yield on the bag label before buying.
Inputs used in this example
- Slab size: 10 ft by 10 ft.
- Thickness: 4 inches.
- Bag yield preset: 80 lb bag at about 0.6 cubic feet.
- Waste factor: 5%.
Expected output
The calculator estimates about 33.33 cubic feet before waste, 35 cubic feet after waste, and about 59 bags when using a 0.6 cubic-foot bag yield.
When to adjust this example
- Use the actual yield printed on your 80 lb bag if it differs from the preset.
- For the same 10x10 slab at 4 inches thick, a 60 lb bag yield of 0.45 cubic feet would be about 78 bags, while a 40 lb bag yield of 0.30 cubic feet would be about 117 bags.
- Increase waste for uneven base preparation, overdig, or hand-mixing losses.
- Large projects may be better reviewed as ready-mix volume instead of individual bags.
Formula explanation
- Convert 4 inches to one-third of a foot.
- Multiply slab length, slab width, and thickness to get cubic feet.
- Apply the waste factor.
- Divide by 0.6 cubic feet per bag and round up.
Main calculator
Use the full Concrete Slab Calculator to change dimensions, waste factor, and optional user-entered unit price.
FAQ
Is every 80 lb concrete bag exactly 0.6 cubic feet?
No. The preset is a planning approximation. Use the yield printed on the specific bag when possible.
Does this calculate labor or delivery?
No. It estimates material quantity only and does not provide live prices, local quotes, or labor costs.
How many 80 lb bags of concrete do I need for a 10x10 slab?
59 80 lb bags for the default 10x10 slab at 4 inches thick with 5% waste. The calculator uses 35.00 cu ft after waste and a 0.60 cu ft yield, so 35 / 0.60 rounds up to 59.
How many 60 lb or 40 lb bags for the same 10x10 slab?
78 60 lb bags or 117 40 lb bags for the same 10x10, 4-inch-thick slab with 5% waste. Those counts use 0.45 cu ft and 0.30 cu ft preset yields, rounded up.
How thick should a 10x10 concrete slab be?
A 4-inch slab is a common planning thickness for light-duty DIY pads. Heavier sheds, vehicle loads, weak soil, or local code may require 6 inches, reinforcement, or a project-specific design.
Is ready-mix cheaper than bags for a 10x10 slab?
This page does not compare live prices. Qualitatively, once a slab is around 1+ cubic yard, ready-mix usually wins on effort and consistency, while bags may still fit small pads or tight access.
Choosing 40, 60, or 80 lb bags
The 80 lb preset keeps the bag count lower, but each bag is heavy. A 60 lb or 40 lb bag can be easier to lift and stage, but you will mix more bags for the same 35.00 cu ft after waste. Always confirm the yield on the bag label before buying.
Related material guides
Use these guides when you want to understand the planning assumptions behind this worked example.
Compare concrete volume and bag counts for a 10 ft by 10 ft slab at common planning thicknesses.
Concrete guide Recommended Concrete Slab Thickness for Patios, Sheds, and DrivewaysLearn how slab thickness affects concrete volume, bag count, and planning assumptions before estimating material quantity.