🗓️ Last updated: May 2026·Calculation assumptions shown below
Material Calculator

🏗️ Concrete Bag Calculator

Find out exactly how many 80 lb, 60 lb, or 40 lb bags you need for slabs, footings, posts, and steps — with cost estimate and ready-mix comparison.

⚙️ Project Type
📐 Slab Dimensions
📏 Standard residential slab thickness: 4 inches. Driveways: 4–6 inches. Garage floors: 4 inches minimum. Sidewalks: 4 inches. Heavy equipment pads: 6+ inches.
⚙️ Bag Options
Bags to Buy
× 80 lb bags
Cubic Feet
Cubic Yards
Est. Bag Cost
Ready-Mix Cost*
*if available in your area
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Frequently Asked Questions

How many bags of concrete do I need?
An 80-pound bag covers approximately 0.6 cubic feet. A 10x10 foot slab at 4 inches thick requires about 50 bags of 80-pound mix.
What thickness should a concrete slab be?
Walkways: 3-4 inches. Driveways and garage floors: 4-6 inches. Patios: 4 inches. Vehicle-bearing slabs should be reinforced with rebar.
How long does concrete take to cure?
Concrete reaches 70% strength in 7 days and full strength at 28 days. Safe to walk on after 24-48 hours, safe for vehicles after 7 days.