🧱 Concrete Calculator
Calculate concrete volume for slabs, footings, columns, stairs, and walls
%
Slab / Patio / Driveway
Footing / Foundation
Column / Pier
Staircase
Retaining Wall / Foundation Wall
Concrete Calculation Results
Volume (cubic feet)
33.3
ft³
Volume (cubic yards)
1.23
yd³
Volume (cubic meters)
0.94
m³
📦 Bag Count (by bag size)
🧪 Material Mix (1:2:3 Ratio)
Cement (94lb bags)
8.5 bags
Sand (cubic feet)
16.7 ft³
Gravel (cubic feet)
25.0 ft³
Water (gallons)
12.5 gal
📋 Concrete Mix Design Guide
Standard Mix
1 : 2 : 3
Cement : Sand : Gravel. Ideal for slabs, footings, and general construction.
Heavy Duty Mix
1 : 1.5 : 2.5
Higher strength for driveways, industrial floors, and heavy traffic areas.
Foundation Mix
1 : 2 : 4
For mass concrete, footings, and foundations where high strength isn't critical.
Semi-Dry Mix
1 : 3 : 5
For paving stones, blocks, and precast elements.
Frequently Asked Questions
How much concrete do I need for a slab?
To calculate concrete for a slab: multiply length (ft) × width (ft) × thickness (ft) ÷ 27 = cubic yards. For example, a 10×10 slab at 4 inches thick needs about 1.23 cubic yards.
How many bags of concrete do I need?
A 60lb bag yields 0.45 cubic feet, 80lb bag yields 0.6 cubic feet. Divide total cubic feet by bag yield. A 10×10 slab at 4 inches needs about 56 80lb bags or 74 60lb bags.
What's the concrete mix ratio for slabs?
Standard slab mix ratio is 1:2:3 (1 part cement, 2 parts sand, 3 parts gravel). For driveways and heavy traffic, use 1:1.5:2.5. For footings, use 1:2:4.
How thick should a concrete slab be?
Patios and walkways: 4 inches. Driveways: 5-6 inches. Garage floors: 6 inches. Heavy vehicle areas: 6-8 inches. Footings: 12-24 inches depending on structure.
How much does concrete cost per yard?
Ready-mix concrete costs $120-$180 per cubic yard on average, including delivery. Small loads may have extra fees. Bags cost $5-$8 per 80lb bag, equivalent to $200-$300 per yard.
How do I calculate concrete for round columns?
For round columns: π × radius² × height. For example, a 12-inch diameter column (0.5 ft radius) at 10 feet tall needs about 7.85 cubic feet (0.29 yards) of concrete.
What's the wastage factor for concrete?
Add 5-10% extra concrete for waste, spillage, and uneven subgrade. For complex projects or first-time pours, use 10%. For simple slabs, 5% is usually sufficient.
How long does concrete take to cure?
Concrete reaches 70% strength in 7 days, 100% in 28 days. Light foot traffic at 3-4 days, vehicle traffic at 7-10 days. Full load capacity after 28 days.