Concrete business guide
Concrete job costing guide
For concrete work, a reliable process should compare estimated and actual labor, material and overhead. Record dimensions, mix, reinforcement, pour date and site condition, and itemize each cubic yard, square foot, labor hour and equipment day that affects the price.
Start concrete job costing with measured length, width and thickness, convert the volume to the supplier’s unit, and state a separate allowance. Then add delivery, reinforcement, formwork, preparation, labor, equipment and finishing rather than treating concrete volume as the whole job price.
Calculate placed volume before ordering
A rectangular slab’s volume is length × width × thickness. Convert thickness into the same length unit first. For dimensions in feet, divide cubic feet by 27 to obtain cubic yards. For dimensions in metres, the result is cubic metres.
A 20 ft × 12 ft slab at an assumed 4-inch thickness is 20 × 12 × (4 ÷ 12) = 80 cubic feet, or about 2.96 cubic yards. An illustrative 10% allowance gives about 3.26 cubic yards before any supplier ordering increment. The allowance is an assumption, not a universal waste requirement.
Cost the full scope
The table lists cost categories to review. Actual thickness, mix, reinforcement and site preparation must follow the project requirements; a volume calculator does not determine structural suitability.
| Cost category | Record or assumption |
|---|---|
| Concrete supply | Quoted delivered quantity and unit price |
| Delivery or small-load charge | Supplier’s actual terms |
| Base preparation and excavation | Measured area, depth and disposal |
| Formwork and reinforcement | Specified quantities and purchase costs |
| Placement and finishing | Crew person-hours and equipment |
| Curing, joints and cleanup | Agreed scope and material needs |
Separate quantities from business profit
Multiply each verified quantity by its actual cost, add job-specific equipment and subcontract work, and allocate overhead consistently. Apply a markup or margin on an explicitly stated cost basis; do not call a 25% markup a 25% margin.
Document access restrictions, pumping, weather assumptions and excluded work before approval. Compare supplier tickets and recorded labor with the estimate afterward. Show customer-approved changes separately, especially where changed dimensions or preparation alter the original volume and cost.
Frequently asked questions
How much concrete is needed for a 20-by-12-foot slab at 4 inches?
The rectangular volume is 80 cubic feet, approximately 2.96 cubic yards, before any allowance or ordering increment. Required thickness and specification must come from the project requirements.
Does concrete volume determine the full job price?
No. Include applicable delivery, preparation, formwork, reinforcement, labor, equipment, finishing, overhead and profit in the defined scope.