16×20 Concrete Slab (4 inches): Yards, Feet & Bags
A 16×20 slab at 4 inches is a common size for patio or gazebo base. It’s usually manageable with bags, but if access is easy you may prefer ready-mix for speed and consistency.
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Quick Answer
Tip: Always confirm the yield printed on your bag label. Bag yield guide
Large pour: consider ready-mix delivery for speed and consistent results. Bag counts this high can take significant mixing time.
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 secure to prevent shifting, especially at the edges.
Finish the surface as desired and keep it moist during curing for best results.
How to Estimate This Slab in 3 Steps
Measure
Length 16 ft, width 20 ft, thickness 4 in.
Compute Volume
Area: 320 sq ft → volume: 106.7 ft³ → 3.95 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 the best option for mixing concrete?
Ready-mix is convenient for larger projects, while bagged concrete allows for flexibility in smaller areas.
How should I prepare the base for my slab?
Excavate to a stable substrate, ensuring it's level and compacted to support the slab's weight.
How do I account for waste when ordering concrete?
Always order a bit extra to cover potential spillage and variations in the base preparation.
What thickness should I choose for my slab?
A thickness of four inches is generally suitable for light to moderate loads, but consider your specific use case.
Related Slab Sizes
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