How deep should a concrete patio slab be poured?

For standard residential pedestrian use like patios and sidewalks, a 4-inch concrete depth is the standard building code minimum. For heavy vehicular loads, hot tubs, driveways, or garage floors, a minimum depth of 6 inches reinforced with #4 rebar or welded wire mesh is recommended.

How much concrete is needed for a standard fence post hole?

A standard 10-inch diameter post hole dug to a depth of 3 feet requires approximately 1.6 cubic feet of concrete, which equals about 2.7 bags of 80lb pre-mixed concrete per post. For light 4x4 line posts, a 8-inch hole requires roughly 2 bags.

When should I order a concrete transit mixer truck instead of bags?

If your project requires more than 1.5 to 2.0 cubic yards (roughly 70 to 90 bags of 80lb concrete), ordering ready-mixed concrete delivered by transit truck is significantly more cost-effective, faster, and ensures uniform compressive strength without cold joints.

How much does a cubic yard of concrete cost in 2026?

In 2026, ready-mix concrete delivered by transit truck averages $135 to $165 per cubic yard for standard 3,000–3,500 psi mix. Short-load fees ($100–$180) typically apply for orders under 5 or 6 cubic yards.

CBCCALC

Volume Estimator

Concrete Volume Calculator

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

One cubic yard contains exactly 27 cubic feet. A single standard 80lb bag of pre-mixed concrete yields approximately 0.60 cubic feet of wet mixed concrete. Therefore, you require exactly 45 bags of 80lb concrete to equal one cubic yard (or 60 bags of 60lb concrete).

Plan slabs, walkways, fence posts, columns, and foundation footings. Estimate concrete in cubic yards, cubic feet, or pre-mixed 80lb/60lb bags instantly under ASTM C94 standards.

Concrete presets

Concrete Structure Shape

Length (ft)

Width (ft)

Thickness (in)

Waste Buffer (%)

Total Concrete Required

Enter dimensions to calculate concrete volume

Concrete Order Guideline

Wet concrete is highly dense ($145$ lbs/cuft). Ordering a ready-mix truck delivery is highly recommended for volumes exceeding $1.0$ cubic yard.

Common Slab Sizes & Concrete Yardage

Project Slab Size	Area (sq ft)	4" Slab (Cu Yds w/ 10%)	6" Slab (Cu Yds w/ 10%)	80lb Bags (4" Slab)
10' × 10' Patio	100	1.36 yd³	2.04 yd³	62 bags
12' × 12' Shed Base	144	1.96 yd³	2.93 yd³	89 bags
12' × 20' 1-Car Driveway	240	3.26 yd³	4.89 yd³	147 bags
20' × 20' 2-Car Garage	400	5.43 yd³	8.15 yd³	245 bags
24' × 24' Workshop Slab	576	7.82 yd³	11.73 yd³	352 bags

How to Calculate Concrete Slab & Footing Volume

Concrete estimation is based on three-dimensional geometry: length, width, and thickness. Follow these step-by-step rules:

Convert Thickness to Feet

Always convert slab thickness from inches to feet by dividing by 12 (4 inches = 0.333 ft; 6 inches = 0.50 ft).

Calculate Cubic Feet

Multiply Length (ft) × Width (ft) × Thickness (ft) = Total Cubic Feet.

Divide by 27 for Cubic Yards

There are exactly 27 cubic feet in one cubic yard. Divide cubic feet by 27.

Include 10% Subgrade Waste

Uneven subgrade excavation and grade pitch always absorb extra concrete. Always add 10%.

Determine Bag Quantities

Multiply cubic yards by 45 for 80lb bags, or by 60 for 60lb bags if mixing on site.

Order Transit Delivery

For pours over 2 cubic yards, arrange a ready-mix truck delivery with 3,000+ psi concrete (ASTM C94).

Concrete Pouring Best Practices

Compacted Subbase: Never pour concrete over organic topsoil or loose fill. Compact 4 inches of crushed aggregate (ASTM D2940) to prevent slab cracking.
Control Joint Spacing: Cut control joints at intervals equal to 24 to 30 times the slab thickness in inches (e.g. 8 to 10 feet apart for a 4-inch slab).
Moisture Curing: Keep newly placed concrete damp for at least 5 to 7 days to reach maximum design compressive strength.
Weather Protection: Do not pour concrete when freezing temperatures (< 40°F) are expected within 48 hours without thermal curing blankets.

2026 Ready-Mix & Bagged Concrete Pricing

In 2026, delivered ready-mix concrete costs $135 to $165 per cubic yard. An 80 lb pre-mix bag costs $5.50 to $7.00 at home improvement stores. Professional flatwork labor costs add $6.00 to $12.00 per square foot for finishing.

Technical Standards & Code Verification ASTM & IRC Verified

Formulas, modular dimensions, and material yields verified by the CinderCalc Technical Team

Editorial Review: March 2026

Calculations aligned with ASTM C94 (Ready-Mix), ACI 318 (Structural Concrete), ASTM C33 (Aggregates), IRC Section R402 specifications.

Verified Against US Building Codes & NCMA TEK Manuals

Masonry Q&A

Concrete Volume & Bag FAQ

Verified answers on bag-to-yard conversions, post hole sizing, and slab thickness standards.

One cubic yard contains exactly 27 cubic feet. A single standard 80lb bag of pre-mixed concrete yields approximately 0.60 cubic feet of wet mixed concrete. Therefore, you require exactly 45 bags of 80lb concrete to equal one cubic yard (or 60 bags of 60lb concrete).