Estimating how much bagged concrete a project needs starts with one number: how many bags of concrete are in a yard. A cubic yard holds 27 cubic feet of material, and the bag count depends entirely on the weight of the bags you buy. A yard of concrete can be built from 90 bags of 40 lb mix, 75 bags of 50 lb mix, 60 bags of 60 lb mix, or 45 bags of 80 lb mix. Contractors and DIY builders use these figures to price driveways, footings, patios, and small slabs before a single bag is ordered.
Bagged concrete is dry ready-mix made from Portland cement, sand, aggregate, water, and approved ingredients, blended before it reaches the job site. Normal ready-mix concrete weighs about 133 lb per cubic foot, which works out to roughly 3600 lb per cubic yard, though the density shifts with the amount of cement, aggregate, and moisture in each batch. Premixed bags suit small and medium projects, and mixing them on site needs only basic tools such as a tray, hoe, wheelbarrow, and shovel. A concrete truck is costly when you need only part of a load, since many suppliers charge a delivery fee on top of the material. For finishing touches around a pour, decorative options like colorful concrete tiles give floors and walls a different look than plain gray concrete.
Bag Counts for a Full Cubic Yard
One cubic yard equals 27 cubic feet, and each bag size yields a fixed fraction of that volume. Dividing 27 by the yield of a single bag gives the total count for the yard. The table below lists the standard counts used across the industry for general-purpose mix.
| Bag weight | Bags per cubic yard | Yield per bag |
|---|---|---|
| 40 lb | 90 | 0.30 cu ft |
| 50 lb | 75 | 0.36 cu ft |
| 60 lb | 60 | 0.45 cu ft |
| 80 lb | 45 | 0.60 cu ft |
| 90 lb | 40 | 0.67 cu ft |
The same volume math applies no matter what you are placing. Filling a plain slab and consolidating concrete in congested reinforced concrete members both start from the same yardage calculation, even though placement gets harder when rebar crowds the formwork and leaves little room for the mix.
Why Bag Weight Changes the Count
A heavier bag does not always mean proportionally more concrete by volume, because the blend matters. Yield depends on the density of the dry mix, the amount of aggregate, and how much water the instructions call for. A 60 lb bag of standard mix yields about 0.45 cubic feet, so 60 bags make a yard. An 80 lb bag yields about 0.60 cubic feet, so 45 bags make the same yard. The pattern extends across the range: 40 lb bags produce 0.30 cubic feet each, 50 lb bags produce 0.36 cubic feet, and 90 lb bags produce about 0.67 cubic feet.
Bags for Two Yards and Beyond
Once the per-yard count is known, larger volumes multiply directly. Two yards need 180 bags of 40 lb mix or 90 bags of 80 lb mix. Three yards need 270 bags of 40 lb mix or 135 bags of 80 lb mix. Five yards, a common truck-minimum volume, works out to 225 bags of 80 lb mix, which is why most contractors order ready-mix delivery at that scale instead of handling hundreds of bags by hand.
Bag Weight, Mix Strength, and What the Numbers Assume
The standard counts assume a general-purpose mix near 4000 psi, the strength specified for most slabs, footings, and patios. Different jobs call for different grades of concrete, and the grade changes the blend proportions even when the bag weight stays the same. A higher-strength mix carries more cement and less aggregate, which shifts the yield slightly.
How Mix Ratio Affects Yield
A mix ratio such as 1:2:4 refers to one part cement, two parts sand, and four parts coarse aggregate by volume, with water added separately at roughly half the cement weight. Changing the ratio changes the density of the finished concrete, and denser mixes yield slightly less volume per bag because more material packs into the same space. Manufacturers print the expected yield on each bag, and that printed value is the number to use for estimating rather than a generic table.
Cement Bags versus Concrete Mix Bags
Portland cement bags are not the same as concrete mix bags. A 94 lb bag of Portland cement equals one cubic foot of cement, so it takes 27 bags to make a cubic yard of pure cement. Cement alone does not make concrete, however. A cubic yard of finished concrete also needs sand, aggregate, and water, so treat the 94 lb cement count and the 40 to 90 lb mix counts as separate calculations, one for cement and one for the full mix.
Calculating Bags for Slabs and Footings
For a slab or footing, find the volume in cubic feet first, then divide by the yield per bag. The method below works a common example: a 10 by 10 foot slab, 4 inches thick.
Volume Math for a Rectangular Pour
- Measure the length, width, and depth of the pour in feet. A 10 by 10 slab at 4 inches thick measures 10 by 10 by 0.33 feet.
- Multiply the three dimensions to get the volume in cubic feet: 10 x 10 x 0.33 equals 33 cubic feet.
- Divide by 27 to convert to cubic yards: 33 divided by 27 equals 1.22 yards.
- Multiply the yardage by the bags-per-yard figure for your bag size from the table. At 45 bags per yard for 80 lb mix, a 1.22-yard slab needs about 55 bags.
Round up rather than down, because bag yields assume perfect placement and real pours lose material to uneven ground, form leaks, and waste in the tray. Adding one extra bag for every 20 planned keeps the job from stopping mid-pour.
Footings follow the same method with different numbers. A continuous footing 20 feet long, 12 inches wide, and 12 inches deep holds 20 cubic feet, or about 0.74 yards, which takes roughly 33 bags of 80 lb mix. Column footings and pier pads are smaller, often under half a bag, so the leftover from a slab pour is usually enough.
Patching and Overlay Jobs
Thin repairs do not need full bags of mix. An 80 lb bag covers roughly 2.5 square feet at 3 inches thick, or about 3.7 square feet at 2 inches. For topping an existing surface, follow the guidance on how to pour new concrete over old concrete so the new layer bonds instead of delaminating, and keep the topping layer thick enough to avoid cracking.
Mixing and Placing Bagged Concrete
Mixing bags on site takes basic tools: a mixing tray, a hoe, a wheelbarrow, and a shovel, or a powered cement mixer for bigger batches. Add water gradually and mix until the color is uniform and no dry pockets remain. Each batch should be placed before the previous one stiffens, because once concrete starts to set, adding water to revive it weakens the final strength.
Step-by-Step Mixing
- Empty the bag into the tray or mixer and form a small crater in the center of the pile.
- Pour in about three-quarters of the water called for on the bag.
- Turn the mix until the water is absorbed, then add the remaining water in small amounts.
- Work the batch within 20 to 30 minutes, before the mix begins to set.
- Clean the tools immediately, since cured concrete is far harder to remove than fresh mix.
After placement, the work is not finished. Inspection and testing of the finished concrete checks for honeycombing, surface defects, and achieved strength, catching problems before the slab goes into service. Small voids found early can be patched, while structural issues found late usually mean demolition and repouring.
Bagged Concrete versus Ready-Mix Delivery
Bagged concrete wins on small jobs, and ready-mix wins on volume. A concrete truck carries about 10 cubic yards, and many suppliers charge a delivery fee even for short loads, so a quarter-yard project makes no sense by truck. Once the pour passes roughly 1.5 to 2 cubic yards, the delivered price per yard starts to beat bags, and the mixing labor disappears.
When to Order a Truck
Order ready-mix when the volume exceeds what a crew can mix and place in one setting. Two or three people can place roughly 30 to 40 bags per hour by hand, which caps practical bagged pours near 1.5 yards. For structural elements such as prestressed concrete members, plant-batched mix delivers consistent strength that field mixing cannot guarantee, since every truckload is proportioned and tested before delivery.
Comparing Costs
Bag prices vary by region and brand, but the comparison usually lands in the same place: bagged concrete costs two to three times more per cubic yard than trucked mix before labor. The trade-off is control, because bags let you mix exactly what you need and avoid paying for a whole truck. For walkways, footings, and thin slabs under a yard, that control is worth the premium.
The bag count for any yardage comes down to one division problem: 27 cubic feet divided by the yield of the bag. Lock in the count for your bag size, then decide between hand mixing and delivery based on total volume. Remember that not every concrete product mixes the same, since lean concrete and normal concrete differ in cement content and behave differently once placed.