Concrete Job Costing Spreadsheet: How to Bid Slabs and Driveways at True Cost
Most concrete bids are built backward. A contractor looks at square footage, guesses a per-yard price based on what worked last time, and quotes the job. The problem: that gut-feel number rarely accounts for the hours equipment and crew sit on site before and after the pour. Here's the method to cost a job correctly, using a 24x30 driveway pour (800 sq ft, 4 inches thick) as the example.
Step 1: Calculate concrete volume and material cost. 800 sq ft x 0.333 ft (4 in) = 266.4 cubic feet, divided by 27 = 9.87 cubic yards. Round up to 10 yards for waste. At $145/yard ready-mix, that's $1,450 in material.
Step 2: Load in mixer truck time, not just delivery. A 10-yard pour typically needs 2 trucks. Each truck isn't just a delivery fee — it includes load time, drive time, and wait time on site if the crew isn't ready to pour immediately. If your ready-mix supplier charges $95/hour after the first hour on site, and each truck sits 45 minutes past the free window, that's an extra $71 per truck, $142 total. Many contractors only enter the flat delivery fee and miss this.
Step 3: Cost the pump, not just rent it. A boom pump for a driveway runs roughly $650-$850 for a half-day rental, plus an operator at $75/hour for 3 hours = $225. Total pump line: $875-$1,075. This gets left off notepad bids entirely, or lumped into "misc" at a guessed flat rate.
Step 4: Cost finishing labor by task, not by day rate. Finishing a driveway this size takes a 3-person crew about 5 hours: screeding, floating, edging, broom finish, and curing application. At a blended $32/hour labor cost (wages plus burden), that's 3 x 5 x $32 = $480.
Step 5: Add equipment wear allocation. Finishing tools, forms, and small equipment depreciate with use. A flat $0.15/sq ft wear allocation on this job = $120. Skipping this line is how tools quietly cost money across a year of jobs even though no single job shows it.
Step 6: Total true cost and compare to quoted price. Material $1,450 + truck overage $142 + pump $975 + labor $480 + wear $120 = $3,167 true cost. If the original bid was based on "$3.50/sq ft x 800 sq ft = $2,800," the job was underbid by $367 before overhead or margin is even added. That's the gap between a gut-feel quote and a costed one.
Step 7: Add overhead and margin last. Once true cost is known, apply a fixed overhead percentage (say 10%) and target margin (say 15%) on top of the $3,167 base — not on top of the original guessed number. This is the difference between pricing a job and hoping a job works out.
A spreadsheet built for this needs to compute: cubic yard volume from dimensions with waste factor, tiered truck time costs based on on-site wait, pump rental plus operator hours as a combined line, task-based finishing labor by crew size and hours, a per-job equipment wear allocation, and a final bid price built from true cost plus overhead and margin — not from a flat per-square-foot guess.