How many 80 lb bags of concrete make a yard?

45 bags of 80 lb premix make 1 cubic yard of concrete. Each 80 lb bag yields 0.60 cubic feet, and 1 cubic yard equals 27 cubic feet, so 27 divided by 0.60 equals 45 bags. Always add 10 percent overage, which brings a practical order to 50 bags per yard to account for waste and uneven subgrade.

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

A 10 by 10 foot slab at 4 inches thick needs 1.23 cubic yards. With a 10 percent waste allowance, order 1.36 cubic yards. That equals 62 bags of 80 lb premix or 37 bags of 90 lb premix. At 5 inches thick, the same slab requires 1.54 cubic yards and 70 bags of 80 lb premix.

Is it cheaper to use bags or order ready-mix concrete?

Ready-mix is cheaper per cubic yard for any pour over about 1 cubic yard. Bagged 80 lb premix costs $270 to $405 per yard in material alone at 2026 retail prices. Ready-mix runs $150 to $220 per cubic yard delivered. The bag route adds labor time and often produces less consistent compressive strength than a plant-mixed batch.

How much water do you add to an 80 lb bag of concrete?

An 80 lb bag of standard premix requires approximately 3 quarts of clean water. Adding more water than the bag calls for raises the water-to-cement ratio above 0.50 and reduces compressive strength, sometimes from 4000 PSI down to 2500 PSI. Mix until the batch is uniform and holds its shape without slumping flat.

How long before you can walk or drive on bagged concrete?

Foot traffic is safe 24 to 48 hours after the pour. Vehicle traffic requires 7 days, when the concrete reaches roughly 70 percent of design strength. Full cure takes 28 days, and heavy or sustained loads should wait until that point. Driving on a slab before 7 days risks surface cracking even if the concrete feels solid.

Does a thicker slab mean more bags per square foot?

Yes. Every additional inch of thickness adds 0.083 cubic feet per square foot of slab area. A 4-inch slab uses 0.333 cubic feet per square foot; a 5-inch slab uses 0.417. Over 100 square feet, that difference is 8.4 cubic feet, or about 14 additional 80 lb bags. Recalculate the total any time the design thickness changes.

How Many Bags of Concrete Are in a Yard?

One cubic yard of concrete requires 45 bags of 60 lb premix, 40 bags of 65 lb premix, or 27 bags of 90 lb premix. Those figures assume zero waste and no variation in mix water, so a 10 percent overage is standard practice on any real job.

The bag count matters because it determines whether mixing by hand is practical or whether ordering ready-mix is the right call. Both paths are covered below, with the arithmetic shown so a reader can apply the numbers to any slab dimension.

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Key facts

45 bags of 60 lb premix or 27 bags of 90 lb premix fill 1 cubic yard of concrete.
1 cubic yard equals 27 cubic feet, the standard unit for ordering ready-mix trucks.
A 4-inch slab uses roughly 1.23 cubic yards per 100 square feet of surface area.
Ready-mix trucks typically deliver a minimum of 1 cubic yard, at $150 to $220 per yard in 2026.
Premix bags cost $6 to $9 each, putting the material cost of 1 yard at $162 to $405 depending on bag size.
Full cure takes 28 days; foot traffic is safe after 24 to 48 hours, vehicle traffic after 7 days.

Why Does 1 Cubic Yard Equal 27 Cubic Feet?

A cubic yard is a cube measuring 3 feet on every side: 3 × 3 × 3 = 27 cubic feet. Concrete volume is always calculated in cubic feet first, then divided by 27 to convert to yards, because ready-mix is priced and delivered by the yard.

The cubic foot is the working unit. A slab that is 10 feet long, 10 feet wide, and 4 inches thick contains 10 × 10 × 0.333 = 33.3 cubic feet, or 1.23 cubic yards. Every bag-count calculation starts from that same arithmetic.

How Many Bags of Concrete Fill 1 Cubic Yard?

At 60 lb per bag, 45 bags fill 1 cubic yard. At 90 lb per bag, 27 bags fill 1 cubic yard. The yield printed on the bag is the governing figure. Quikrete 60 lb bags yield 0.45 cubic feet each. Quikrete 80 lb bags yield 0.60 cubic feet. Quikrete 90 lb bags yield approximately 1.0 cubic feet per bag for high-strength mixes.

Bag-count reference by size

Four common bag sizes cover most retail and commercial premix products. The yields below reflect standard 3000 PSI to 4000 PSI premix bags.

Bag weight	Yield per bag (cu ft)	Bags per cubic yard
40 lb	0.30	90
60 lb	0.45	60
80 lb	0.60	45
90 lb	1.00	27

Note: 40 lb bags are not practical for any poured slab. Ninety bags to the yard means 90 trips to the mixer. The 80 lb bag is the standard site bag because one person can carry the bag and still mix by hand in a drum or wheelbarrow.

How Do You Calculate Bags for a Specific Slab?

Multiply length in feet by width in feet by thickness in feet, divide by 27 to get cubic yards, then multiply by the bag count per yard for your chosen bag size. Add 10 percent to account for uneven subgrade and spillage.

Worked example: 12 × 12 foot patio at 4 inches thick

Step 1. Convert thickness to feet: 4 inches ÷ 12 = 0.333 feet.
Step 2. Calculate volume: 12 × 12 × 0.333 = 47.95 cubic feet.
Step 3. Convert to yards: 47.95 ÷ 27 = 1.78 cubic yards.
Step 4. Add 10 percent waste: 1.78 × 1.10 = 1.96 cubic yards, rounded to 2 cubic yards.
Step 5. Bag count at 80 lb: 2 × 45 = 90 bags.

Ninety 80 lb bags weigh 7,200 lb total. That is the point where most contractors stop and call a ready-mix supplier.

Worked example: 10 × 10 foot shed pad at 4 inches thick

Volume: 10 × 10 × 0.333 = 33.3 cubic feet, or 1.23 cubic yards. With 10 percent waste, 1.36 cubic yards. At 80 lb per bag, that is 62 bags. At 90 lb per bag, 37 bags. This is a reasonable one-day bag job for two people with a rented drum mixer.

When Does Bagged Concrete Make Sense and When Does Ready-Mix Win?

Bagged concrete is practical for slabs up to roughly 1 cubic yard, or about 80 square feet at 4 inches thick. Beyond that volume, mixing by hand becomes slower than the concrete can be placed cleanly, which leads to cold joints and surface defects.

Ready-mix trucks in 2026 charge $150 to $220 per cubic yard for standard 3500 PSI mix in the Gulf South region, with a typical minimum load of 1 cubic yard and short-load surcharges of $50 to $150 for loads under 3 yards. Bagged 80 lb premix runs $6 to $9 per bag retail. At 45 bags per yard, that is $270 to $405 per yard in material alone, before labor and equipment rental.

For anything larger than a 10 × 10 slab, ready-mix is almost always cheaper per yard and produces a more consistent mix with better compressive strength control. Bag mixes are convenient, not economical at volume.

What Are the Most Common Mistakes When Working With Bagged Concrete?

Adding too much water is the single most common error, and it directly reduces compressive strength. A standard 80 lb bag calls for approximately 3 quarts of water. Adding a fourth quart drops the yield strength from 4000 PSI to roughly 2500 PSI as the water-to-cement ratio increases beyond 0.50.

Three other frequent errors affect the finished slab:

Underestimating volume. Running short mid-pour creates a cold joint, a visible seam where the first batch began to set before the second batch was placed. Cold joints are a structural weak point and cannot be repaired by surface patching.
Skipping the overage allowance. Subgrade that is 1 inch lower than planned across a 12 × 12 area adds 1.33 cubic feet of extra volume. Always order or buy 10 percent more than the calculated amount.
Moving vehicle traffic too early. Bagged premix reaches roughly 70 percent of design strength at 7 days. Parking a vehicle on a 4-day-old slab can cause surface cracking even if the concrete feels hard. Full 28-day cure is required before sustained heavy loads.

Does Ground Condition Change the Calculation for Greater New Orleans Projects?

The bag count stays the same, but the slab thickness often increases because of soft subgrade. Greater New Orleans sits on alluvial clay and organic silt with a high water table across the south shore, Metairie, and most of Jefferson Parish. That soil consolidates under load and does not provide the bearing capacity that sandy or gravelly soil does.

In practice, slabs poured on soft fill or organic material in this region often call for 5 inches of concrete rather than 4, and for 6 inches of compacted limestone base rather than 4. A 5-inch slab at 100 square feet requires 1.54 cubic yards instead of 1.23 cubic yards, meaning 7 additional 80 lb bags per 100 square feet. On a larger pour, that difference is significant enough to recalculate before buying material.

Rebar sizing and spacing also change on soft ground. A residential driveway on stable soil might use #3 rebar on 24-inch centres; the same driveway over organic fill in New Orleans East or the West Bank commonly uses #4 rebar on 18-inch centres. Those decisions belong to the contractor or engineer reviewing the site, not to a bag-count formula.

Should You Do This Yourself or Hire a Contractor?

A slab under 50 square feet at 4 inches thick, with no reinforcement requirement and stable soil underneath, is a manageable DIY job for someone comfortable with physical labor. That is roughly 24 bags of 80 lb premix, a rented drum mixer, and a long screed board.

A slab larger than 100 square feet, any slab that requires rebar, any pour on fill soil, and any slab with a garage apron or vehicle loading calls for a contractor. The reasons are sequencing, labor, and equipment: a crew of 3 can place, screed, and finish 10 cubic yards in a single morning. Two people with a drum mixer cannot, and a slab poured in two sessions on separate days without proper joint treatment will crack at the seam.

If the project is in Greater New Orleans and the subgrade is unknown, a contractor assessment before ordering anything, bags or ready-mix, prevents the most expensive mistakes.

New Orleans Concrete Contractors provides free site assessments for residential and commercial projects across Greater New Orleans, Jefferson Parish, and surrounding areas. Contact the office to describe the project and get a straight answer on whether bags, ready-mix, or a full pour crew fits the job.

Common questions

How many 80 lb bags of concrete make a yard?: 45 bags of 80 lb premix make 1 cubic yard of concrete. Each 80 lb bag yields 0.60 cubic feet, and 1 cubic yard equals 27 cubic feet, so 27 divided by 0.60 equals 45 bags. Always add 10 percent overage, which brings a practical order to 50 bags per yard to account for waste and uneven subgrade.
How many bags of concrete do I need for a 10x10 slab?: A 10 by 10 foot slab at 4 inches thick needs 1.23 cubic yards. With a 10 percent waste allowance, order 1.36 cubic yards. That equals 62 bags of 80 lb premix or 37 bags of 90 lb premix. At 5 inches thick, the same slab requires 1.54 cubic yards and 70 bags of 80 lb premix.
Is it cheaper to use bags or order ready-mix concrete?: Ready-mix is cheaper per cubic yard for any pour over about 1 cubic yard. Bagged 80 lb premix costs $270 to $405 per yard in material alone at 2026 retail prices. Ready-mix runs $150 to $220 per cubic yard delivered. The bag route adds labor time and often produces less consistent compressive strength than a plant-mixed batch.
How much water do you add to an 80 lb bag of concrete?: An 80 lb bag of standard premix requires approximately 3 quarts of clean water. Adding more water than the bag calls for raises the water-to-cement ratio above 0.50 and reduces compressive strength, sometimes from 4000 PSI down to 2500 PSI. Mix until the batch is uniform and holds its shape without slumping flat.
How long before you can walk or drive on bagged concrete?: Foot traffic is safe 24 to 48 hours after the pour. Vehicle traffic requires 7 days, when the concrete reaches roughly 70 percent of design strength. Full cure takes 28 days, and heavy or sustained loads should wait until that point. Driving on a slab before 7 days risks surface cracking even if the concrete feels solid.
Does a thicker slab mean more bags per square foot?: Yes. Every additional inch of thickness adds 0.083 cubic feet per square foot of slab area. A 4-inch slab uses 0.333 cubic feet per square foot; a 5-inch slab uses 0.417. Over 100 square feet, that difference is 8.4 cubic feet, or about 14 additional 80 lb bags. Recalculate the total any time the design thickness changes.

Last updated August 5, 2026

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