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

A cubic yard is 27 cubic feet. At 0.60 ft3 per 80 lb bag: 27 / 0.60 = 45 bags per cubic yard. For 60 lb bags (0.45 ft3 each): 60 bags per yard. For 50 lb bags (0.375 ft3): 72 bags per yard.

How many bags of concrete do I need for a 10x10 slab?

A 10x10 ft slab at 4 inches thick = 33.3 ft3 = 1.23 cubic yards. With 10% waste: approximately 62 bags of 80 lb concrete, or 74 bags of 60 lb.

How many bags of concrete for a post hole?

A standard 12-inch diameter post hole at 36 inches deep = approximately 2.36 ft3. At 0.60 ft3 per 80 lb bag: 4 bags per hole (rounded up with waste).

When should I use ready-mix instead of bags?

For pours over 1-2 cubic yards, ready-mix is usually faster and often cheaper. A cubic yard requires 45 bags of 80 lb concrete. Ready-mix minimums are typically 1 yard with a delivery charge.

Concrete Bag Calculator – How Many Bags of Concrete Do I Need?

Length (ft)

Width (ft)

Thickness (in)

Waste (%)

Typical: 10% for most pours. Common thickness: patios 4 in, driveways 4-6 in.

Bag size focus

Select a size to apply a price and highlight that row.

Price per bag (optional)

Applies to the selected bag size only.

Concrete Bag Calculator: Bags, Weight & Coverage Guide

This calculator estimates how many bags of concrete you need for slabs, post holes, footings, and pads. Enter dimensions on the slab or post hole tab, or enter a known volume directly. Results show bag counts for all sizes (40, 50, 60, and 80 lb), total weight, estimated water, and optional material cost.

How many bags of concrete per cubic yard?

Bag size	Yield per bag	Bags per cubic yard	Weight per yard	Typical price/bag (2026)
40 lb	0.30 ft³	90 bags	3,600 lb	$4–$6
50 lb	0.375 ft³	72 bags	3,600 lb	$5–$7
60 lb	0.45 ft³	60 bags	3,600 lb	$5–$8
80 lb	0.60 ft³	45 bags	3,600 lb	$6–$10

Yields vary slightly by product and mix design. Check your bag label. 60 and 80 lb bags highlighted as most common for DIY projects.

Concrete bags by project size

Project	Volume	80 lb bags	60 lb bags	Ready-mix?
Fence post (12" dia × 36" deep)	2.4 ft³ / 0.09 yd³	4 bags	6 bags	No (use bags)
10×10 ft patio, 4 in thick	33.3 ft³ / 1.23 yd³	62 bags	74 bags	Borderline
12×12 ft patio, 4 in thick	48 ft³ / 1.78 yd³	88 bags	107 bags	Consider ready-mix
20×20 ft driveway, 4 in thick	133 ft³ / 4.94 yd³	246 bags	296 bags	Yes (order ready-mix)
10×20 ft garage floor, 6 in thick	100 ft³ / 3.70 yd³	185 bags	222 bags	Yes (order ready-mix)

Includes 10% waste. Ready-mix typically becomes cost-effective over 1.5-2 cubic yards depending on local delivery minimums.

Bags vs ready-mix

For most DIY projects under 1 cubic yard, including fence posts, small pads, footings. Bagged concrete is the practical choice. No minimum order, no delivery scheduling, and you can mix at your own pace. For pours over 1.5-2 cubic yards, the maths shift: a cubic yard requires 45 bags of 80 lb concrete, each needing to be mixed separately. At that volume, ready-mix saves significant labour time and often costs less once you factor in bags, rental mixer, and your time.

Frequently Asked Questions

Divide your total cubic feet by the yield per bag, then round up. An 80 lb bag yields 0.60 ft³. For a 10×10 ft slab at 4 inches thick: 10 × 10 × (4÷12) = 33.3 ft³ ÷ 0.60 = 56 bags. Add 10% waste = 62 bags. The calculator above handles this instantly.

Exactly 45 bags of 80 lb concrete per cubic yard (27 ft³ ÷ 0.60 ft³/bag). For 60 lb bags: 60 per yard. For 50 lb bags: 72 per yard. For 40 lb bags: 90 per yard.

A 10×10 ft slab at 4 inches thick = 33.3 ft³ = 1.23 cubic yards. With 10% waste: approximately 62 bags of 80 lb or 74 bags of 60 lb. At this size, consider ordering ready-mix to avoid mixing 60+ bags by hand.

A standard 12-inch hole at 36 inches deep = 2.36 ft³. At 0.60 ft³ per 80 lb bag: 4 bags per hole (rounded up with waste). Use the Post Holes tab above for a total across all holes.

For pours over 1.5-2 cubic yards, ready-mix is usually faster and often cheaper. A yard of concrete = 45 bags of 80 lb. Mixing by hand takes several hours. Ready-mix minimums are typically 1 yard with a delivery fee.

Most 80 lb bags require 3-4 quarts (0.75-1 gallon) of water. 60 lb bags need about 3 quarts. Always follow the manufacturer's label. Adding too much water is the most common DIY mistake and significantly weakens the finished concrete.

Use 10% for most pours. Use 5% for simple rectangular slabs with clean formwork. Use 15% for complex shapes or multiple small pours. It's always better to have one extra bag than run short mid-pour.

Concrete Bag Planning Checklist

Reviewed by Maria Ramirez, PE. Covers site prep, formwork, reinforcement, ordering, mixing procedure, and curing steps.

Download Checklist (PDF)

Planning reference only. See Methodology and Data Sources. View all project checklists →

Accuracy & Review

Reviewed by: Maria Ramirez, PE

Maria is a licensed Professional Engineer with experience in residential and light commercial concrete quantity takeoffs. She reviewed the formulas, unit conversions, rounding rules, and default yield assumptions used in this calculator.

Last updated: Feb 12, 2026

See: Methodology · Data Sources · Review Board

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Disclaimer: Results are for general planning only and do not constitute engineering or structural design advice. Actual quantities vary based on site conditions, slab thickness, reinforcement, and local code requirements.

See Methodology and Data Sources for details.