Accurately estimate concrete bags, cubic yards, and total cost for slabs, footings, columns, block fill, and mortar — based on USA standard bag sizes and ASTM measurements.
Last Updated: January 2025 • Reviewed by Licensed Concrete Contractor
Concrete Slab — Top & Side View
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Continuous Footing — 3D View
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Round Column — Side View
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CMU Block Wall — Cores Shown in Yellow
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Brick/Block Wall — Mortar Joints Highlighted
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Project Settings
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Calculation Results
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Bags Needed
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Cubic Feet
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Cubic Yards
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Estimated Cost
USA Standard Concrete Bag Yields
The table below shows how much volume each standard USA concrete mix bag produces, based on manufacturer specifications (QUIKRETE, Sakrete, etc.).
Bag Size
Yield (cu ft)
Bags per Cubic Yard
Typical Use
80 lb
0.60 cu ft
45 bags
Slabs, footings, general purpose
60 lb
0.45 cu ft
60 bags
Smaller projects, repairs
90 lb
0.67 cu ft
40 bags
High-strength applications
40 lb
0.30 cu ft
90 bags
Small patches, DIY projects
Common Concrete Projects — Quick Reference
Typical concrete quantities for popular residential projects using 4-inch slab thickness and 80 lb bags.
10 × 10 Patio
1.24 cu yd 56 bags (80 lb) 4″ thickness
12 × 12 Shed Floor
1.78 cu yd 80 bags (80 lb) 4″ thickness
20 × 20 Driveway
4.94 cu yd 223 bags (80 lb) 4″ thickness
24 × 24 Garage Slab
7.11 cu yd 320 bags (80 lb) 6″ thickness
4 × 50 Walkway
0.74 cu yd 34 bags (80 lb) 4″ thickness
8″×16″×8″ Footing (per LF)
0.025 cu yd/LF 1.1 bags/LF (80 lb) Standard footing
How This Calculator Works
Our calculator uses standard geometric formulas aligned with ASTM C94 and ACI 318 guidelines — the same standards followed by licensed concrete contractors across the United States.
The thickness is converted from inches to feet by dividing by 12. The result in cubic feet is then divided by 27 to get cubic yards — the standard unit for ordering ready-mix concrete in the USA.
Based on the BIA (Brick Industry Association) method, approximately 0.017 cu yd of mortar per 100 sq ft of wall surface for standard 3/8″ joints.
Waste Factor
Industry standard practice (per ACI guidelines) adds 5–15% extra material to account for spillage, over-excavation, uneven subgrade, and variations in dimensions. We recommend 10% for most projects.
Frequently Asked Questions
How many 80lb bags of concrete are in a cubic yard?
A cubic yard (27 cubic feet) of concrete requires approximately 45 bags of 80lb concrete mix. This is calculated as 27 ÷ 0.60 = 45 bags. Each 80lb bag yields 0.60 cubic feet when mixed with water per manufacturer specifications.
How much does an 80lb bag of concrete cover?
One 80lb bag yields 0.60 cubic feet of concrete. At 4 inches thick, this covers approximately 1.8 square feet. At 6 inches thick, it covers about 1.2 square feet. Coverage depends on the pour thickness.
How many bags of concrete do I need for a 10×10 slab?
For a 10×10 foot slab at 4 inches thick, you need approximately 56 bags of 80lb concrete (1.24 cubic yards). At 6 inches thick, you need about 83 bags (1.85 cubic yards). Always add 10% waste factor for real-world conditions.
When should I order ready-mix concrete instead of using bags?
The general rule of thumb: if your project requires more than 40 bags (approximately 1 cubic yard), ordering ready-mix concrete from a local batch plant is usually more cost-effective and labor-efficient. Ready-mix also ensures consistent quality and proper mixing for larger pours.
What is the standard slab thickness for different projects?
Per IRC (International Residential Code) and ACI standards: Patio/walkway: 4 inches | Driveway: 5–6 inches | Garage floor: 6 inches | Foundation slab: 6–8 inches. Local building codes may require minimum thickness with reinforcement requirements.
How much does a yard of concrete cost in 2025 (USA)?
As of 2025, the average cost of ready-mix concrete in the USA ranges from $140 to $180 per cubic yard, depending on your location, mix design (psi strength), and delivery distance. Short-load fees may apply for orders under 3 cubic yards. An 80lb bag typically costs $4.50 to $6.50 at home improvement stores.
How many concrete blocks does an 80lb bag of mortar fill?
One 80lb bag of masonry mortar mix is sufficient to lay approximately 25–30 standard 8×8×16 CMU blocks with 3/8″ joints. This equals roughly 35–40 square feet of wall surface. For pure block core fill (grout), one 80lb bag fills approximately 1.7 standard two-core blocks.
Is this calculator accurate for building permits?
This calculator provides reliable estimates based on standard geometric formulas and manufacturer-published bag yields. However, for building permit applications, you should have a licensed engineer or architect verify calculations. Local building departments may have specific requirements for concrete quantity documentation.
CC
Concrete Contractors Advisory Team
Reviewed by licensed concrete professionals with 20+ years of field experience in residential and commercial construction across the United States.
Expert Verified • ASTM/ACI Compliant
References & Standards
ASTM C94 — Standard Specification for Ready-Mixed Concrete
ASTM C90 — Standard Specification for Loadbearing Concrete Masonry Units
ACI 318 — Building Code Requirements for Structural Concrete
ACI 304 — Guide to Measuring, Mixing, Transporting, and Placing Concrete
IRC (International Residential Code) — Chapter R506 Concrete Floors
QUIKRETE Technical Data Sheets — Bag Yield Specifications (2024)
Portland Cement Association (PCA) — Concrete Basics Publication
Brick Industry Association (BIA) — Technical Notes on Mortar
Disclaimer: This calculator provides estimates for planning purposes only. Actual concrete quantities may vary based on site conditions, subgrade preparation, formwork accuracy, concrete slump, and waste factors beyond the selected percentage. Always consult with a licensed contractor or engineer for critical structural projects. We are not liable for any discrepancies between estimated and actual material requirements.
