One Bag of Quikrete Covers How Many Square Feet

You're planning a small concrete project—maybe a 6x8 patio or a walkway—and trying to figure out how many bags of Quikrete to buy. The bag says it yields "0.6 cubic feet," but you think in square feet. How do you translate that into actual coverage for your project? And does thickness matter?

Quick Answer: One 80lb bag of Quikrete covers 1.8 square feet at 4 inches thick (standard slab depth). A 60lb bag covers 1.35 square feet, a 50lb bag covers 1.1 square feet, and a 40lb bag covers 0.9 square feet—all at 4-inch thickness. Coverage increases proportionally as thickness decreases. Always buy 10% extra to account for waste and uneven subgrade.

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Complete Coverage Chart by Bag Size

Here's the definitive reference for all Quikrete bag sizes at common thicknesses. Bookmark this table—you'll use it for every project.

How to use this chart:

Find your bag size and thickness. That number tells you how many square feet one bag covers. Divide your total square footage by that number to get bags needed. For a 10x10 slab (100 sq ft) at 4 inches thick using 80lb bags: 100 ÷ 1.8 = 56 bags.

Understanding the Math

The coverage calculation is straightforward once you understand the relationship between cubic feet and square feet at different thicknesses.

The Formula

Coverage (square feet) = Bag yield (cubic feet) ÷ Thickness (feet)

Example with 80lb bag at 4 inches thick:

• Bag yield: 0.6 cubic feet
• Thickness: 4 inches = 0.33 feet
• Coverage: 0.6 ÷ 0.33 = 1.8 square feet

This means one 80lb bag spreads over 1.8 square feet when poured 4 inches deep. Double the thickness to 8 inches, and that same bag only covers 0.9 square feet—half the area.

Why Thickness Matters So Much

Thickness dramatically affects how many bags you need. Here's what happens to one 80lb bag at different depths:

• 1 inch thick: Covers 7.2 square feet (thin overlay or topping)
• 2 inches thick: Covers 3.6 square feet (walkways, stepping stones)
• 3 inches thick: Covers 2.4 square feet (light-duty patios)
• 4 inches thick: Covers 1.8 square feet (standard slabs, patios)
• 6 inches thick: Covers 1.2 square feet (driveways, heavy loads)

The difference between 3 inches and 4 inches doesn't sound like much, but it changes your material needs by 33%. For a 100 square foot project, that's the difference between 42 bags and 56 bags—a $60 difference and an extra trip to the store.

Real Project Examples

Let's calculate actual bag requirements for common DIY projects using 80lb bags at standard thicknesses.

Project 1: 8x10 Patio Slab (4 inches thick)

• Area: 80 square feet
• Coverage per bag: 1.8 square feet
• Bags needed: 80 ÷ 1.8 = 44.4 bags
• Round up: 45 bags
• Add 10% safety margin: 50 bags
• Total cost: $275 (at $5.50/bag)

Project 2: 3x20 Walkway (3 inches thick)

• Area: 60 square feet
• Coverage per bag: 2.4 square feet
• Bags needed: 60 ÷ 2.4 = 25 bags
• Add 10% safety margin: 28 bags
• Total cost: $154 (at $5.50/bag)

Project 3: Four 2x2 Stepping Stones (2 inches thick)

• Area: 16 square feet total (4 stones × 4 sq ft each)
• Coverage per bag: 3.6 square feet
• Bags needed: 16 ÷ 3.6 = 4.4 bags
• Round up: 5 bags
• Total cost: $28 (at $5.50/bag)

Project 4: 12x12 Shed Base (6 inches thick)

• Area: 144 square feet
• Coverage per bag: 1.2 square feet
• Bags needed: 144 ÷ 1.2 = 120 bags
• Add 10% safety margin: 132 bags
• Total cost: $726 (at $5.50/bag)

Important note: For projects requiring more than 60-80 bags, ready-mix concrete delivery becomes more economical. A concrete truck delivers 1 cubic yard (27 cubic feet) for $150-200, equivalent to 45 bags of 80lb mix at $248. Use our concrete cost calculator to compare bagged vs ready-mix pricing for your project size.

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Choosing the Right Bag Size

Quikrete offers multiple bag sizes for good reason—different projects benefit from different weights. Here's how to choose.

Bag Size Decision Matrix

Cost per cubic foot comparison:

• 40lb bag: $11.67 per cubic foot
• 50lb bag: $11.33 per cubic foot
• 60lb bag: $10.56 per cubic foot
• 80lb bag: $9.17 per cubic foot (most economical)

The 80lb bags offer the best value, saving about 20% compared to 40lb bags. For a project requiring 20 cubic feet of concrete, that's a $50 savings. But only choose 80lb bags if you can handle the weight safely.

Factors That Affect Coverage

The coverage numbers in our chart assume ideal conditions. Several factors can reduce actual coverage:

Uneven Subgrade

If your base isn't perfectly level, low spots require more concrete. A base that varies by just 1 inch across a 10x10 area adds 8.3 cubic feet—equivalent to 14 extra bags of 80lb mix. This is why proper base preparation matters. Always compact and level your gravel base before calculating concrete needs.

Form Flex and Bulging

Forms bow outward under concrete weight, especially on larger slabs. This can add 5-10% to your concrete requirements. Stake forms every 2-3 feet and use sturdy 2x4 or 2x6 lumber to minimize flex.

Mixing Waste

Some concrete inevitably sticks to your mixing container, wheelbarrow, and tools. Hand-mixing wastes more than machine mixing. Budget for:

• Hand-mixing in wheelbarrow: 10% waste
• Electric mixer: 5% waste
• Gas-powered mixer: 3% waste

Spillage and Overfill

First-time DIYers often overfill forms slightly or spill concrete during transport. This is normal and expected. The 10% safety margin we recommend accounts for these losses.

Thickness Guidelines by Application

Choosing the right thickness ensures your project lasts. Too thin and it cracks prematurely. Too thick and you waste money. Here are the standards recommended by the American Concrete Institute:

Never go thinner than minimum thickness to save money. The cost difference between 3 inches and 4 inches on a 100 square foot patio is about $75 in materials, but a failed slab costs $2,000+ to replace.

When to Switch to Ready-Mix

Bagged concrete makes sense for small projects, but there's a break-even point where ready-mix becomes smarter.

Break-Even Analysis

Cost comparison for 10x10 slab (4 inches thick):

Bagged concrete (80lb bags):

• Bags needed: 56 bags
• Material cost: $308 (at $5.50/bag)
• Mixing time: 6-8 hours
• Physical effort: Very high
• Quality consistency: Variable

Ready-mix delivery (1.25 yards):

• Concrete cost: $150-200
• Delivery fee: $75-100
• Total cost: $225-300
• Pour time: 30 minutes
• Physical effort: Moderate
• Quality consistency: Excellent

The decision point:

For projects under 1 cubic yard (27 cubic feet, or about 100 square feet at 4 inches), bags make sense. Above that, ready-mix saves time, effort, and often money. For projects requiring 80+ bags, ready-mix is almost always the better choice.

Use our concrete slab calculator to determine your project's cubic yardage, then compare costs using our cost estimator.

Common Coverage Mistakes

Mistake #1: Forgetting thickness in calculations

Many DIYers calculate square footage but forget to account for thickness. A 10x10 area isn't 100 cubic feet— it's only 33 cubic feet at 4 inches thick. Always convert thickness to feet (4 inches = 0.33 feet) before calculating volume.

Mistake #2: Using coverage for wrong thickness

The bag might say "covers 0.6 cubic feet," but that doesn't tell you square footage unless you know thickness. Always refer to a coverage chart or calculate: bag yield ÷ thickness in feet = square feet covered.

Mistake #3: Not buying extra

Buying exactly the calculated amount guarantees you'll run short. Forms flex, bases have low spots, and some concrete gets wasted. Always add 10% to your calculated needs, or 15% if you're inexperienced.

Mistake #4: Mixing all bags at once

Concrete starts setting within 30-90 minutes. Only mix what you can place in that timeframe. For large projects, work in sections and mix bags as needed.

Quick Reference: Bags Needed for Common Projects

Save this reference for quick estimates (using 80lb bags):

• 6x8 patio (4"): 27 bags
• 8x10 patio (4"): 45 bags
• 10x10 patio (4"): 56 bags
• 12x12 patio (4"): 80 bags → Consider ready-mix
• 10x20 driveway (4"): 112 bags → Definitely use ready-mix
• 3x20 walkway (3"): 25 bags
• Four 2x2 stepping stones (2"): 5 bags

Final Recommendations

For most DIY projects, 80lb bags of Quikrete offer the best balance of coverage and economy. One bag covers 1.8 square feet at standard 4-inch thickness. Calculate your square footage, divide by 1.8, and add 10% extra.

For projects requiring more than 60-80 bags, seriously consider ready-mix concrete delivery. The time and effort savings alone justify the cost, and you'll get more consistent quality.

Always verify your calculations with our concrete bags calculator before buying materials. Input your exact dimensions and thickness to get precise bag counts. And remember—it's better to have one extra bag than to run short mid-project. Extra concrete can always be used for stepping stones, test samples, or small repairs.