YardCompute / Project Guides / Concrete Order Quantity
How Much Concrete Should You Order?
Once you calculate the volume of a slab, pad, footing, or other concrete project, you still need to turn that measurement into a practical order quantity. The key steps are keeping units consistent, converting cubic feet to cubic yards, reviewing site conditions, and confirming the final order with the supplier.
1. Calculate the actual concrete volume
For a rectangular slab or pad:
Volume = length × width × thickness
When length and width are in feet, convert thickness from inches to feet by dividing by 12.
2. Convert cubic feet to cubic yards
Ready-mix concrete is commonly ordered in cubic yards. Since one cubic yard equals 27 cubic feet:
Cubic yards = cubic feet ÷ 27
For example, 80 cubic feet is about 2.96 cubic yards.
3. Review the shape and site conditions
A simple rectangular calculation may not represent the entire pour. Add separate calculations for thickened edges, footings, steps, beams, or other sections. Uneven subgrade and over-excavation can also increase actual volume.
4. Consider a planning allowance
A modest allowance can help account for measurement variation, minor waste, and uneven conditions. YardCompute's standard slab calculator uses 10% as a planning estimate, but that is not a universal ordering rule.
For an 80 cubic-foot calculated volume:
80 × 1.10 = 88 cubic feet
88 ÷ 27 ≈ 3.26 cubic yards
The appropriate quantity can be higher or lower depending on the actual project and supplier guidance.
5. Confirm supplier requirements
Before ordering ready-mix, confirm the supplier's minimum order, delivery charges, mix specification, required strength, slump or other project requirements, and any local delivery constraints. Suppliers may also recommend a particular ordering quantity based on their experience with the project.
6. Do not treat the calculator as the purchase order
A calculator provides a planning estimate. The final order should account for the actual formed dimensions, site conditions, project specifications, and supplier requirements. For structural work, follow the plans and applicable professional or local requirements.
Common mistakes
- Ordering cubic feet when the supplier sells by cubic yard.
- Forgetting to convert inches of thickness into feet.
- Ignoring thickened edges, steps, footings, or other separate sections.
- Assuming 10% is always the correct allowance.
- Failing to confirm supplier minimums and mix requirements.
Use the Concrete Calculator
The YardCompute Concrete Calculator estimates volume, applies a 10% planning allowance, and converts the result to cubic yards. For a detailed measurement walkthrough, see How to Calculate Concrete for a Slab.
FAQ
How many cubic feet are in a cubic yard?
One cubic yard equals 27 cubic feet.
Should I always add 10% to a concrete order?
No. Ten percent is a simple planning allowance used by the YardCompute slab calculator. Actual ordering needs depend on the project and supplier.
What if my concrete project has footings and a slab?
Calculate each distinct section separately, then add the volumes before applying any appropriate planning allowance.
Do concrete suppliers require whole cubic yards?
Ordering rules vary by supplier. Ask the supplier how they quote and deliver partial-yard quantities and whether a minimum order applies.
Should I verify the final quantity?
Yes. Confirm dimensions, mix requirements, minimums, delivery conditions, and final quantity with the concrete supplier or qualified professional.
Planning estimate disclaimer
Estimates are for planning purposes only. Actual material requirements may vary based on site conditions, material specifications, installation methods, waste, and local requirements. Always verify quantities with your supplier or qualified professional before purchasing materials.