Concrete Slab Calculator

Calculate cubic yards of concrete needed for a slab from length, width, and thickness, plus the number of 60lb or 80lb bags and total cost.

Frequently Asked Questions

How many 80lb bags of concrete are in a yard?

About 45 bags. An 80lb bag yields roughly 0.60 cubic feet when mixed; one cubic yard equals 27 cubic feet, so 27 / 0.60 = 45 bags. Bagged concrete costs $5-7 per bag, making it competitive only for small jobs.

How thick should a driveway slab be?

4 inches is standard for passenger cars on stable soil. 5 inches for SUVs/trucks. 6 inches if heavy trucks or RVs will use it. Reinforce with wire mesh or rebar in all cases for crack resistance over a 30+ year life.

How long until concrete is walkable?

24 hours for foot traffic with care. 7 days for normal walking. 28 days for full cured strength (3,000+ psi). Light vehicles can drive on at 7 days; heavy vehicles wait the full 28 days.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.