How many 20 kg bags in a cubic meter?
About 104 standard 20 kg bags make 1 m³ of concrete (range 100–110). Round up and add waste.
A standard 20 kg bag yields roughly 0.0096 m³ of mixed concrete, so 1 m³ ÷ 0.0096 ≈ 104 bags.
| Volume | 20 kg bags |
|---|---|
| 0.5 m³ | ≈ 52 |
| 1.0 m³ | ≈ 104 |
| 1.5 m³ | ≈ 156 |
How many 80 lb bags in a cubic yard?
About 45 bags of 80 lb per cubic yard.
An 80 lb bag yields about 0.6 ft³. One cubic yard is 27 ft³, so 27 ÷ 0.6 = 45 bags.
Post hole concrete formula
V = π × r² × depth per hole, × number of holes, × 1.10 for waste.
r is half the hole diameter. Example: 30 cm diameter, 90 cm deep → r = 0.15 m, V = π × 0.0225 × 0.9 ≈ 0.064 m³ per hole.
Slab concrete formula
V = length × width × thickness, × 1.10 for waste.
Example: 4 m × 3 m × 0.10 m = 1.2 m³ net, 1.32 m³ with waste.
How much gravel for 10 x 10 ft, 4 in deep?
Net 33.3 ft³ = 1.23 yd³. Order about 1.36 yd³ with 10% waste.
10 × 10 × 0.333 = 33.3 ft³; 33.3 ÷ 27 = 1.23 yd³; × 1.1 = 1.36 yd³.
Convert m³ to bags or yards
1 m³ = 1.308 yd³ ≈ 104 bags of 20 kg ≈ 45 bags of 80 lb per yd³.
| Convert | Value |
|---|---|
| m³ → yd³ | × 1.308 |
| yd³ → m³ | × 0.7646 |
| m³ → 20 kg bags | × 104 |
| yd³ → 80 lb bags | × 45 |
- Post holes (cylinder):
V = π × (d/2)² × depth× number of holes. - Slab (rectangular):
V = length × width × thickness. - Fill: same volume formula; weight uses bulk density (gravel ≈ 1.6 t/m³, sand ≈ 1.4 t/m³).
- Waste: fixed 10% →
V_total = V × 1.10. - Bags: ≈ 104 × 20 kg bags per m³; ≈ 45 × 80 lb bags per yd³.
- Results are estimates. Confirm structural and mix requirements with a professional.
Home Alone DIY · Free estimator only · Not professional engineering advice. Local mix designs, densities and bag yields vary; always verify with your supplier.