How Many Bags of Concrete for an 8x10 Slab? (~49 Bags @ 4 in)
An 8×10 foot slab covers 80 square feet — a common shed pad or narrow side-yard patio. At standard 4-inch thickness you need about 49 eighty-pound bags; at 6 inches, about 74. Full volume math for both depths below using the same 10% waste factor as our 10×10 and 10×12 slab guides.
Last updated: July 13, 2026
Use the Slab Calculator →Steps
- Calculate base volume — Multiply 8 ft × 10 ft × (thickness in ÷ 12). A 4-inch slab = 26.67 ft³; a 6-inch slab = 40 ft³.
- Add 10% waste — Multiply base volume by 1.10. A 4-inch slab becomes 29.33 ft³; a 6-inch slab becomes 44 ft³.
- Convert to 80 lb bags — Divide adjusted volume by 0.60 ft³ per 80 lb bag and round up. Result: 49 bags (4 in) or 74 bags (6 in).
4-inch slab, 80 sq ft pad
Area: 8 ft × 10 ft = 80 ft². Thickness 4 ÷ 12 = 0.333 ft.
Base volume = 80 × 0.333 = 26.67 ft³. With 10% waste: 26.67 × 1.10 = 29.33 ft³.
Bags = 29.33 ÷ 0.60 = 48.9 → round up to 49 bags of 80 lb mix (~1.09 yd³ with waste).
6-inch slab, heavier load
Same 80 ft² area; thickness 6 ÷ 12 = 0.5 ft. Base volume = 80 × 0.5 = 40 ft³.
With 10% waste: 40 × 1.10 = 44 ft³. Bags = 44 ÷ 0.60 = 73.3 → round up to 74 eighty-pound bags.
Verify with the calculator
Enter 8 ft length, 10 ft width, and your thickness in our free slab calculator for an instant bag count and cubic yard total.
Frequently asked questions
- How many 80 lb bags for an 8x10 patio at 4 inches?
- About 49 bags. Volume is 8 × 10 × (4 ÷ 12) = 26.67 ft³. With 10% waste that is 29.33 ft³. At 0.60 ft³ per 80 lb bag, divide and round up to 49 bags.
- How many bags for an 8x10 slab at 6 inches?
- About 74 bags. Base volume is 40 ft³; with 10% waste 44 ft³. At 0.60 ft³ per bag, 44 ÷ 0.60 = 73.3 → round up to 74 eighty-pound bags.
- 8x10 vs 10x10, how many fewer bags?
- An 8×10 pad is 80 sq ft vs 100 sq ft for 10×10 — about 20% less concrete. At 4 inches you save roughly 13 bags (49 vs 62).
- When is ready-mix cheaper than bags for 8x10?
- A 4-inch 8×10 pour is about 1.09 yd³ with waste — still often bag territory. At 6 inches (~1.63 yd³) compare a short-load truck quote before hauling 74 bags.