How Many Bags of Concrete for a 10×10 Slab?
Exact bag counts for a 10 ft × 10 ft slab in 80, 60 and 40 lb premix bags at 3.5, 4, 5 and 6 inches thick — with the math shown so you can check it.
Quick answer
A 10×10 ft slab, 4 inches thick, is 33.3 ft³ (1.23 yd³) of concrete. That takes 56 bags of 80 lb premix, 75 bags of 60 lb, or 112 bags of 40 lb — before waste. With a 10% allowance, buy 62 × 80 lb bags.
Formula & worked math
Cubic yards = Volume(ft³) ÷ 27
Bags = Volume(ft³) ÷ bag yield(ft³), rounded up
- Area: 10 × 10 = 100 ft²
- Volume at 4 in: 100 × 4 ÷ 12 = 33.33 ft³ (÷ 27 = 1.235 yd³)
- 80 lb bags: 33.33 ÷ 0.60 = 55.56 → 56
- 60 lb bags: 33.33 ÷ 0.45 = 74.07 → 75
- 40 lb bags: 33.33 ÷ 0.30 = 111.11 → 112
- With 10% waste (80 lb): 55.56 × 1.10 = 61.11 → 62
Bags for a 10×10 slab at common thicknesses
Each bag cell shows exact need / with 10% waste, both rounded up.
| Thickness | ft³ | yd³ | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3.5 in | 29.2 | 1.08 | 49 / 54 | 65 / 72 | 98 / 107 |
| 4 in | 33.3 | 1.23 | 56 / 62 | 75 / 82 | 112 / 123 |
| 5 in | 41.7 | 1.54 | 70 / 77 | 93 / 102 | 139 / 153 |
| 6 in | 50.0 | 1.85 | 84 / 92 | 112 / 123 | 167 / 184 |
Want a different size or your own waste percentage? Use the concrete bag calculator or get cubic yards for a ready-mix order from the concrete slab calculator.
Assumptions
- Bag yields are the figures printed on standard premix bags: 80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 40 lb ≈ 0.30 ft³. Check your brand's bag — some high-strength or fast-setting mixes differ.
- The slab is a flat rectangle of uniform thickness on a level, compacted base. Thickened edges, sloped subgrade or low spots add volume.
- Bag counts are always rounded up. The "+10%" column covers spillage, form bulge and an uneven base; 5–10% is a common allowance.
Bags or ready-mix for a 10×10?
At 1.23 yd³, this slab is right around the point where many contractors switch from bags to a ready-mix truck (roughly 1 yd³, or about 45 × 80 lb bags). 62 bags of 80 lb weigh about 2.5 US tons — several trips for a pickup and a lot of hand-mixing, so a mixer rental and a helper are worth planning for. Many ready-mix suppliers have a minimum order or short-load fee, so price both before deciding; bagged concrete also needs to be placed fast enough that each batch blends into the last one.
FAQ
How many 80 lb bags of concrete do I need for a 10x10 slab?
At 4 inches thick, 56 bags exactly (33.3 ft³ ÷ 0.60), or 62 with a 10% waste allowance.
How many cubic yards is a 10x10 slab 4 inches thick?
100 × 4 ÷ 12 = 33.3 ft³, and 33.3 ÷ 27 = 1.23 cubic yards.
How many 60 lb bags for a 10x10 slab?
75 bags at 4 inches (33.33 ÷ 0.45 = 74.07), before waste. At 6 inches it is 112.
Last updated: October 12, 2026.