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How Many Bags of Concrete for a 8' × 10' Slab (4" Thick)?

Instant Pre-Solved Contractor Answer (US Standards)

You need 49 bags of 80-lb concrete (0.99 cubic yards / 26.67 cu ft) including standard 10% waste. Or use 66 bags of 60-lb Quikrete.

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📐 Slab Dimensions & Specifications

10 ft
2 ft 30 ft 60 ft
12 ft
2 ft 30 ft 60 ft
Instant Material Requirement

74 bags (80lb Quikrete)

Total Volume

1.48 cu yd

40 cu ft

Includes 10% waste Total Weight: 5,920 lbs Rebar: 205 lin ft

Dynamic Cross-Section Diagram

10' × 12' × 4"
Compacted Native Subgrade 4" Compacted Gravel Sub-Base (#57 Stone) Poured Concrete Slab (4" Thick · 4,000 PSI) #4 Rebar 10' Length × 12' Width

🛒 Material Shopping List (US Retail SKUs)

80 lb Quikrete Concrete Bags 0.60 cu ft yield per bag
60 lb Quikrete Concrete Bags 0.45 cu ft yield per bag
#4 Rebar (1/2" Deformed Steel) 18" on-center grid + 10% overlap
~11 sticks (20') 205 linear feet
#57 Crushed Stone Sub-Base 4" compacted gravel lift
2.07 tons Bulk yard supply
👷‍♂️

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📐 Exact US Engineering Formula Breakdown

// 1. Calculate Gross Cubic Feet (Volume) Cubic Feet = Length (8') × Width (10') × [Depth (4") ÷ 12] Cubic Feet = 26.67 cu ft // 2. Convert to Cubic Yards (Standard US Unit) Cubic Yards = Cubic Feet ÷ 27 Cubic Yards = 0.99 cu yd // 3. Pre-Mixed Bag Yields (with 10% Waste Factor) 80-lb Bag Count = (26.67 ÷ 0.60 cu ft/bag) × 1.10 = 49 bags 60-lb Bag Count = (26.67 ÷ 0.45 cu ft/bag) × 1.10 = 66 bags 40-lb Bag Count = (26.67 ÷ 0.30 cu ft/bag) × 1.10 = 98 bags // 4. #4 (1/2") Steel Rebar Grid (18" on-center spacing + 10% overlap) Total Linear Feet = ~148 linear feet

Cost Comparison: DIY Materials vs. Turnkey Professional Installation

2026 US Contractor Averages
Option / Method Quantity / Specs Estimated Cost Labor Hours
DIY: 80-lb Quikrete Bags (Home Depot) 49 bags @ $7.48/bag $367 8 hrs
DIY: Ready-Mix Truck Delivery 0.99 cu yd @ $185/yd + short load fee $303 2 hrs
Licensed Concrete Contractor (Turnkey) Excavation, forms, rebar, pour, finish $850 Turnkey

Contractor Installation & Engineering Guide: How Many Bags of Concrete for a 8' × 10' Slab (4" Thick)?

💡 Jobsite Recommendation

A 8×10 ft slab at 4" thick yields 0.99 cubic yards (26.7 cu ft). When ordering materials, always include a 10% overage for uneven soil grading. Pour over a 4" compacted gravel base (#57 crushed stone) and place #4 rebar on an 18" grid elevated with 2" rebar chairs.

1. Engineering Specifications & Material Requirements

When executing a project of this scale, relying on standard generic rules of thumb leads to premature cracking, settling, or water backup. For structural pours and hardscaping, every cubic yard weighs approximately 4,000 lbs, exerting substantial compressive dead loads onto the sub-grade. Ensuring appropriate compressive strength (standard 4,000 PSI at 28-day cure for outdoor slabs, or 3,000 PSI for post hole collars) guarantees structural integrity against vehicle loading, frost heaves, and seasonal thermal expansion.

2. Sub-Base Excavation & Compaction Protocol

Over 80% of outdoor construction failures originate beneath the material layer rather than within the concrete or timber itself. Remove all organic topsoil, sod, and loose clay until reaching solid undisturbed subsoil. For flatwork and paver bases, install a minimum 4-inch lift of #57 crushed limestone or dense grade aggregate (#411 crusher run). Compact the base aggregate in maximum 2-inch lifts using a mechanical gas-powered vibratory plate compactor, maintaining a steady 1/4-inch per foot slope away from building foundations for positive water runoff.

3. Step-by-Step Installation & Application Sequence

  • Layout & Staking: Establish perimeter lines with mason's string and batter boards. Check diagonal squareness using the 3-4-5 Pythagorean theorem before driving form stakes.
  • Forming & Reinforcement: Secure 2×4 or 2×6 dimensional lumber forms with duplex nails. Elevate rebar grid (#4 1/2" deformed steel) on 2-inch plastic chairs to embed steel in the bottom third of the tension zone.
  • Pouring & Consolidation: Deposit material continuously to prevent cold joints. Consolidate with a mechanical pencil vibrator or edge screed to eliminate internal honeycombing and air pockets.
  • Finishing & Texture: Screed flush with forms, bull float immediately to bring paste to the surface, and delay final brooming or edging until all bleed water has evaporated.

4. US Building Code, Permitting & Local Inspections

Under the US International Residential Code (IRC) and local municipal building ordinances, projects exceeding specific square footage or depth thresholds frequently require zoning permits and inspection sign-offs:

  • Frost Line Depth: Post footings and structural foundations must extend below local frost depth (typically 36" to 48" in northern states, 12" to 24" in southern states) to avoid frost-jack displacement.
  • Permit Thresholds: Flatwork within 5 feet of property lines, accessory buildings exceeding 120 sq ft, or electrical mini-split branch circuits typically require municipal permits and licensed trade sign-offs.
  • Call Before You Dig: Dial 811 at least 48 to 72 business hours before excavating to locate underground gas, power, fiber, and water mains free of charge.

5. Pro Contractor Tips to Prevent Costly DIY Pitfalls

Never add excess water to speed up concrete mixing or epoxy pouring—each additional gallon of water per yard drops concrete strength by approximately 500 PSI and causes severe surface scaling. When working in temperatures above 85°F, use shade tarps or morning pour schedules to prevent flash-setting. Apply a curing compound or damp burlap blanket for at least 7 continuous days to maximize full design strength.

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❓ Frequently Asked Questions: How Many Bags of Concrete for a 8' × 10' Slab (4" Thick)?

You need 49 bags of 80lb Quikrete for a 8×10 ft slab at 4" thick, including 10% waste.
For 0.99 cubic yards, hand-mixing bagged concrete in a rented electric barrel mixer is cost-effective.
You need approximately 148 linear feet of #4 (1/2") rebar for an 18" on-center grid pattern, including 10% splice overlap.
Excavate 8 inches total: 4 inches for a compacted gravel sub-base plus 4 inches for the concrete slab.