Which concrete calculator do I need?
| Project | Use this calculator | Quick check |
|---|---|---|
| Patio, pad, footing, solid steps | Slab / footing calculator | 10×10×4" ≈ 1.23 yd³ (~62 × 80 lb after 10% waste) |
| Fence or sign post holes | Post hole calculator | 8"×2 ft ≈ 2 × 80 lb bags after waste |
| Cardboard column forms | Sonotube calculator | 12"×4 ft ≈ 6 × 80 lb bags before waste |
How to choose bag mix vs ready-mix
Bagged QUIKRETE / Sakrete-style mixes suit posts, small pads, and repairs you can place in batches. Past about one cubic yard—or any pour that must be continuous across a large slab—compare the cost and labor of ready-mix delivery. YardTally bag counts use published standard-mix yields of about 0.30 / 0.45 / 0.60 cu ft for 40 / 60 / 80 lb bags; lightweight and high-yield products differ, so read the label.
Worked example: 10×10 patio
Volume = 10 × 10 × (4÷12) = 33.33 cu ft ≈ 1.23 cu yd. With the default 10% waste factor that becomes 36.7 cu ft → 62 bags of 80 lb mix or 82 bags of 60 lb mix. Order gravel base separately with the gravel calculator. Full charts: how many bags of concrete, fence post concrete, and 10×10 slab.
Waste, frost, and regional caveats
Uneven subgrade and spillage routinely consume 5–10% extra on DIY bag mixes. Frost-line depth, soil type, and local code control hole depth and slab thickness—this hub estimates volume only. Confirm reinforcement, joints, and base with local practice before you pour.