🧱 Slab Cost Calculator
Enter the slab dimensions and your prices for concrete, labor, and formwork to estimate the total cost, broken down by concrete (with a 10% waste allowance), labor, and forms.
🧱 Estimate Your Slab Cost
What is a Slab Cost Calculator?
A slab cost calculator turns the size of a concrete slab and a few unit prices into a budget. It works out the concrete volume with a waste allowance and prices it per cubic yard, then adds labor and formwork priced per square foot to total the job.
Enter the length, width, and thickness along with your concrete, labor, and formwork rates to see each cost line and the grand total. These are estimates for planning; verify with a structural engineer for load-bearing work and get firm quotes from local suppliers.
❓ Frequently Asked Questions
How much does a concrete slab cost?
Slab cost is the sum of concrete, labor, and formwork. Concrete is priced per cubic yard against the slab's volume plus a waste allowance; labor and formwork are usually priced per square foot. A 20 × 20 ft, 4-inch slab holds about 5.4 cubic yards with waste, so at $150 a yard the concrete alone is roughly $815 before labor and forms.
What drives the cost of a slab?
Thickness and area set the concrete volume, which is the biggest single line, and the per-yard price swings with your region and the mix strength. Labor and formwork per square foot cover excavation, forming, placing, finishing, and stripping. Reinforcement, a vapor barrier, and pumping are extras to add on top.
Why is a 10% waste allowance added to the concrete?
Subgrade is never perfectly flat, forms flex, and some concrete is lost to spillage and the chute, so the volume you order should exceed the theoretical figure. The calculator adds 10% to the slab volume before pricing concrete so the estimate reflects what you will actually pay for and pour.
Are these slab cost numbers exact?
They are estimates for planning; verify with a structural engineer for load-bearing work and get firm quotes from local suppliers and contractors. Prices vary by region, season, and project size, and this tool only totals the inputs you enter — it does not include permits, site prep, or reinforcement unless you fold them into the rates.