TOOL 03 / FREE · NO SIGNUP
Concrete Calculator
Calculate pour volume and an editable allowance. Add bag yield only when you need a purchase count.
Worked example loaded. These are example measurements and product assumptions.
THE METHOD
How to use this estimate
- Measure the shape you will fill. A round column or slab uses π × radius² × height or thickness.
- The allowance is applied to volume first. Bag count is then rounded up once using the product’s mixed yield.
- Ready-mix ordering is shown as volume. Bags are an alternative estimate and do not need to be ordered alongside ready-mix.
rectangular volume = length × width × thickness; order = volume × quantity × (1 + allowance / 100)
A worked example
The “Load worked example” button uses the same inputs as this example. Explicit unit suffixes keep their meaning in either unit system.
- Input method
- Measured dimensions
- Pour shape
- Slab / footing / rectangular wall
- Length
- 15 ft
- Width / perpendicular height
- 10 ft
- Thickness / column height
- 4 in
- Identical pours
- 1
- Waste allowance
- 10
- Yield per bag
- 0.45 ft3
- Measured volume
- 1.416 m³ / 50 ft³
- Bags
- 123
- Purchased yield
- 1.567 m³ / 55.35 ft³
- Estimated extra yield
- 0.01 m³ / 0.35 ft³
Questions, answered
Why does 1 m³ with 10% allowance and 0.009 m³/bag need 123 bags?
1 × 1.10 ÷ 0.009 = 122.222…; rounding the final purchase gives 123.
Can I combine pours?
Use the optional additional measured volume. The identical-pour multiplier applies to their combined base volume.
Sources and product assumptions
These references explain units or product specifications. Your selected product label takes priority; none of these sources endorses this calculator.
- QUIKRETE Concrete Mix No. 1101 — approximate mixed yield by bag size (PDF) ↗
- Sakrete 5000 Plus — product-specific bag yields ↗
- NIST volume conversions ↗
Source check: 4 October 2026. Worked examples use stated, editable assumptions.