Concrete Bag Calculator
Estimate how many bags you need for slabs, footings, or round pours — free web tool with waste allowance. The iPhone app is built for the same bag math when you are away from a browser.
Concrete bag estimator
Slab, footing, or round pour — choose bag yield and waste.
Bags to order
- Exact bags
- Volume
- Cubic yards
- Waste volume
App screenshots
Real Concrete Bag Calculator screens from the App Store listing.
How to use this calculator
- Select project shape and enter dimensions in consistent units.
- Choose a bag size preset (40–80 lb) or match your bag label yield.
- Set waste percent for spill, uneven subgrade, or partial bags.
Features
- Slab, footing, and round pours
- 40–80 lb bag presets
- Waste percentage options
- Cubic feet and cubic meters
- Rounds up for purchase quantity
- Offline iPhone workflow
Formula
Volume = L × W × D (or πr² × D for rounds). Bags = ceil(volume × (1 + waste%) ÷ bag yield).
10 × 10 ft slab, 4 in thick, 60 lb bags
Net volume ≈ 33.3 ft³. At 0.45 ft³ per bag and 10% waste, plan on about 82 bags (rounded up).
Practical notes
- Bag yields vary by mix and manufacturer — use the value printed on your product.
Take it to the job site
Use Concrete Bag Calculator on your iPhone for fast repeat calculations and the full native workflow — wherever you're working.
Related calculators
Related guides
- How Many Bags of Concrete Do I Need? — Estimate bag count from pour volume and bag yield.
- Concrete Bags for Post Holes — Estimate bags for round post-hole footings.
- 80 lb vs 60 lb Concrete Bags — How bag size changes count for the same pour.
- Concrete Slab Volume Basics — Cubic feet and yards for rectangular slabs.
FAQ
Why round up bag count?
Partial bags are not sold; rounding up avoids coming up short on the pour.
Order volume is an estimate. Confirm with your supplier and account for pump, wheelbarrow, and edge waste.