Concrete Calculator Guide

Calculating the right amount of concrete for your project is essential for budgeting and ordering materials. This calculator helps you determine how much concrete you need for various shapes and applications.

Common Concrete Projects

Concrete Slabs

Slabs are flat horizontal surfaces used for patios, sidewalks, driveways, and foundations. Standard thickness varies:

• Patios & sidewalks: 4 inches (10 cm)
• Driveways (cars): 5-6 inches (12-15 cm)
• Driveways (trucks): 6-8 inches (15-20 cm)
• Garage floors: 4-6 inches (10-15 cm)

Footings

Footings are the foundation that supports walls, columns, and structures. They distribute weight to the soil and prevent settling. Typical footings are 12-24 inches wide and 8-12 inches deep.

Columns & Posts

Concrete columns provide vertical support for decks, pergolas, and fences. Standard residential post holes are 8-12 inches in diameter and 24-48 inches deep, depending on frost line.

Stairs

Concrete stairs require careful calculation. Standard dimensions are:

• Rise (height): 7-8 inches (18-20 cm)
• Run (depth): 10-12 inches (25-30 cm)
• Width: 36-48 inches minimum (90-120 cm)

Ordering Tips

• Add 10% extra: Always order 10% more than calculated to account for spillage, waste, and uneven ground.
• Ready-mix vs bags: For projects over 1 cubic yard, consider ordering ready-mix concrete delivered by truck.
• Bag sizes: Pre-mixed concrete bags come in 40, 60, and 80-pound sizes. Larger bags are more economical but heavier to handle.

Concrete Mix Types

• Standard mix: 2,500-3,000 PSI - suitable for most residential projects
• High-strength mix: 4,000-5,000 PSI - for driveways and heavy loads
• Fast-setting: Sets in 20-40 minutes - good for posts and repairs
• Crack-resistant: Contains fibers to reduce cracking

Weather Considerations

Concrete should be poured when temperatures are between 50-85°F (10-30°C). Cold weather slows curing, while hot weather can cause cracking. Avoid pouring if rain is expected within 24 hours.