8×20 Concrete Slab (4 inches): Yards, Feet & Bags
An 8 ft x 20 ft concrete slab at 4 inches thick works well for a patio or gazebo base. Decide between bags or ready-mix based on your site access and waste factor.
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Quick Answer
Tip: Always confirm the yield printed on your bag label. Bag yield guide
Project Notes (Unique)
Round to 0.25 yd³ when ordering and check yield on the label to ensure you have enough material.
Ensure your base is well-prepped and forms are securely in place to prevent shifting during pouring.
Finish the surface as desired and allow it to cure properly for optimal strength and durability.
How to Estimate This Slab in 3 Steps
Measure
Length 8 ft, width 20 ft, thickness 4 in.
Compute Volume
Area: 160 sq ft → volume: 53.3 ft³ → 1.98 yd³.
Add Waste
Add a small buffer for spillage and uneven subgrade, then round up when ordering.
Planning Notes
Common uses: patio, gazebo base, walkway section.
For more context and conversions, see the Concrete Calculator hub.
Frequently Asked Questions
What’s better for my project: bags or ready-mix concrete?
Bags offer flexibility for smaller projects, while ready-mix is more efficient for larger slabs, especially when access is easier.
How should I prepare the base for my concrete slab?
Clear the area of debris, level the ground, and compact it to create a stable foundation for the slab.
What thickness should I choose for my concrete slab?
A thickness of inches is generally suitable for patios and walkways, but consider the load and usage to determine if more is needed.
How can I minimize waste when ordering concrete?
Estimate your needs carefully and account for a buffer to avoid running short, especially if using bags which can be less forgiving.
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