One number answers every coverage question: at a given thickness, a cubic yard always covers the same area, 324 divided by the thickness in inches. This post is the chart built on that number, in both directions, plus bag coverage for small jobs.
One cubic yard covers 81 sq ft at 4 inches thick, 108 sq ft at 3 inches, 65 sq ft at 5 inches and 54 sq ft at 6 inches. The rule behind every figure: coverage = 324 ÷ thickness in inches. An 80 lb bag covers 1.8 sq ft at 4 inches.
The 324 Rule
Yards needed = Area (sq ft) × thickness (in) ÷ 324, then add 5–10% waste
Why 324? A cubic yard is 27 ft³. Sliced 1 inch thick (1/12 ft), it spreads over 27 ÷ (1/12) = 324 sq ft. Every extra inch of thickness divides that area down proportionally. With this one rule you never need the chart, but the chart is faster.
Coverage Chart by Thickness
| Thickness | Coverage per 1 yd³ | Typical use |
|---|---|---|
| 2 in | 162 sq ft | Overlays, toppings |
| 3 in | 108 sq ft | Light-duty pads |
| 4 in | 81 sq ft | Patios, walkways, shed bases |
| 5 in | 65 sq ft | Driveways, heavier vehicles |
| 6 in | 54 sq ft | Garage floors, RV pads |
| 8 in | 41 sq ft | Footings, heavy-duty slabs |
| 10 in | 32 sq ft | Thickened edges, heavy footings |
| 12 in | 27 sq ft | Deep footings |
The Reverse Chart: Yards for Your Area
| Area | Yards @ 4 in | Yards @ 6 in | With 10% waste @ 4 in |
|---|---|---|---|
| 100 sq ft (10×10) | 1.23 | 1.85 | 1.36 |
| 200 sq ft (10×20) | 2.47 | 3.70 | 2.72 |
| 400 sq ft (20×20) | 4.94 | 7.41 | 5.43 |
| 500 sq ft | 6.17 | 9.26 | 6.79 |
| 1,000 sq ft | 12.35 | 18.52 | 13.58 |
Sanity-check any row: 1,000 sq ft at 4 in = 1,000 × (4 ÷ 12) = 333.3 ft³ ÷ 27 = 12.35 yd³. Two mixer loads, since a truck carries 8–10 yards, the kind of thing worth knowing before the pour is booked, and exactly what the Cubic Yards Calculator confirms for your real dimensions.
Bag Coverage
| Bag | Yield | Covers @ 3 in | Covers @ 4 in | Covers @ 6 in |
|---|---|---|---|---|
| 80 lb | 0.60 ft³ | 2.4 sq ft | 1.8 sq ft | 1.2 sq ft |
| 60 lb | 0.45 ft³ | 1.8 sq ft | 1.35 sq ft | 0.9 sq ft |
| 50 lb | 0.375 ft³ | 1.5 sq ft | 1.1 sq ft | 0.75 sq ft |
| 40 lb | 0.30 ft³ | 1.2 sq ft | 0.9 sq ft | 0.6 sq ft |
Bag coverage is yield ÷ thickness in feet, 0.60 ÷ (4 ÷ 12) = 1.8 sq ft for the 80 lb bag at 4 in. It is the fastest way to sanity-check a bag count in the store aisle: area ÷ coverage per bag, rounded up.
FAQs
How much does a yard of concrete cover at 4 inches?
81 square feet. One cubic yard is 27 ft³, and at 4 in (1/3 ft) thick, 27 ÷ 1/3 = 81 sq ft. The general rule is 324 ÷ thickness in inches.
How many yards do I need for 500 sq ft at 4 inches?
6.17 yd³ exact, 6.79 yd³ with 10% waste. Work it as area × thickness ÷ 324: 500 × 4 ÷ 324 = 6.17. The Cubic Yards Calculator does it for any area and thickness.
How much area does a full concrete truck cover?
A 10 yd³ load covers about 810 sq ft at 4 inches, 650 sq ft at 5 inches or 540 sq ft at 6 inches, multiply the per-yard coverage by the load size.
Why does my real pour use more than the chart says?
The chart assumes a perfectly level base at exact thickness. Real bases dip, forms bow and edges over-dig, all of which add volume. That is what the 5–10% waste allowance is for, the chart gives exact volume, you order chart-plus-waste.
Does coverage change with the mix strength?
No. Coverage is pure geometry, a cubic yard is 27 ft³ whatever its psi rating. Strength changes price and performance, never volume.
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Sources used for standards and conversions: 1 yd³ = 27 ft³; US bagged-concrete manufacturers’ printed yields. National Ready Mixed Concrete Association (NRMCA) ordering guidance.
Disclaimer: Coverage figures are exact-volume geometry. Always add a waste allowance for real site conditions before ordering.