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Concrete is the one material where running short is a real problem instead of an inconvenience. Come up half a yard shy on a slab and you get a cold joint across the middle of your patio that will crack along that line for the rest of its life. The calculator below converts slab, footing, wall, and post hole dimensions into cubic feet, cubic yards, bag counts, and a 2026 price for both bagged mix and ready-mix delivery, so you know before you start whether this is a mixer job or a truck job.
Concrete Calculator
At 1.36 cubic yards, call a ready-mix truck. Mixing 62 bags by hand is a full day of work and a cold joint risk.
Volume before waste: 33.3 cu ft. Bag yields assume 0.30, 0.45, and 0.60 cu ft for 40, 60, and 80 lb bags. Ready-mix priced at $150-$185 per cubic yard delivered plus a $60-$80 per yard short-load fee under the 4-yard minimum. Materials only, no base prep, rebar, forms, or labor.
The Math Behind It
Every concrete calculation is the same idea: get the volume into cubic feet, then divide by 27 to get cubic yards, because a cubic yard is 3 feet by 3 feet by 3 feet. The only thing that changes is how you get the volume, and the only thing that trips people up is that thickness is quoted in inches while everything else is in feet.
- Slab: cubic feet = length (ft) × width (ft) × thickness (in) ÷ 12
- Footing or wall: cubic feet = run length (ft) × height (in) ÷ 12 × width (in) ÷ 12
- Round column or post hole: cubic feet = 3.1416 × (diameter in inches ÷ 24)² × depth (ft)
- Then: cubic yards = cubic feet ÷ 27, and bags = cubic feet ÷ bag yield
Work the classic example, a 10x10 patio at 4 inches. Volume is 10 × 10 × (4 ÷ 12), which is 33.3 cubic feet. Divide by 27 and you get 1.23 cubic yards. A 60 lb bag yields 0.45 cubic feet, so 33.3 ÷ 0.45 is 74, call it 75 bags of 60 lb mix. Add the standard 10% waste factor and you are at 36.7 cubic feet, 1.36 cubic yards, 82 bags of 60 lb or 62 bags of 80 lb. That is the number you actually buy.
Bag yields are printed on the bag and they are consistent across brands: 0.30 cubic feet for a 40 lb bag, 0.45 for a 60 lb bag, and 0.60 for an 80 lb bag. Fast-setting mix comes in 50 lb bags that yield about 0.375 cubic feet. Nothing about the mix design changes the arithmetic, only the working time.
| Pour | Cubic feet | Cubic yards | 60 lb bags |
|---|---|---|---|
| 10x10 patio, 4 in | 33.3 | 1.23 | 75 |
| 12x12 patio, 4 in | 48.0 | 1.78 | 107 |
| 24x24 garage floor, 4 in | 192.0 | 7.11 | Order ready-mix |
| 20x20 driveway, 5 in | 166.7 | 6.17 | Order ready-mix |
| 40 ft footing, 8 in deep x 16 in wide | 35.6 | 1.32 | 79 |
| 12 in post hole, 3 ft deep | 2.4 | 0.09 | 6 |
| 4x4 shed pad, 4 in | 5.3 | 0.20 | 12 |
Add your waste factor on top of these. One cubic yard weighs roughly 4,000 lb, so a 7 yard driveway pour is about 14 tons of concrete.
Bags vs Ready-Mix: Where the Line Is
The crossover is right around one cubic yard. Below it, bags are cheaper and infinitely more convenient. Above it, ready-mix is cheaper per yard, arrives in one homogeneous batch, and saves you a day of work that you will feel for a week.
The reason people over-buy bags is that a cubic yard does not sound like much. It is 45 bags of 80 lb mix, 3,600 lb of dry material, roughly $315 in bags, and about six hours of mixing for two people with a rented mixer. That same yard delivered is around $165 plus a short-load fee. By two yards, the bag route is 90 bags and a genuinely bad Saturday.
| Volume | Buy | Why |
|---|---|---|
| Under 0.25 cu yd | Bags, mixed in a wheelbarrow or tub | Post holes, mailbox bases, small repairs |
| 0.25-1 cu yd | Bags, rented mixer ($60-$90 per day) | Shed pads, short walkways, deck footings |
| 1-2 cu yd | Judgment call | Ready-mix is close on price and far better concrete |
| 2-4 cu yd | Ready-mix, expect a short-load fee | Patios, garage floors, aprons |
| 4+ cu yd | Ready-mix, no short-load fee | Driveways, additions, full slabs |
Some suppliers also rent trailer-mounted mixers, sold by the yard, which split the difference around 1-2 yards.
The other thing bags cost you is consistency. Every batch you mix by hand has its own water content, and water content is what sets strength. A truck delivers one uniform load batched to a spec you can name on the ticket. For most residential flatwork that spec is 3,500 to 4,000 psi with a 4 to 5 inch slump, air entrained at 5-7% anywhere that freezes. Bagged pre-mix is typically labeled 4,000 psi at 28 days if you follow the water instructions on the bag, and noticeably weaker if you do not.
The short-load fee nobody quotes you
Ready-mix suppliers price around a full truck. Most set a minimum of 4 to 5 cubic yards and charge $60-$80 for every yard you are short of it, sometimes as a flat $150-$250 instead. Order 1.5 yards and your $250 of concrete arrives with a $175 fee attached. That is not a scam, it is the cost of sending a truck and a driver out for a partial load, but it is the number that makes small pours feel expensive. If a neighbor is pouring too, splitting one truck is the cheapest concrete either of you will ever buy.
Slab Thickness Guide
Thickness drives volume linearly, so going from 4 inches to 6 inches is a 50% larger order. Thicker is not automatically better either: a 6 inch slab on a soft, unprepared subgrade will still crack, while a 4 inch slab on 6 inches of compacted stone will not. Spend the money on base before you spend it on depth.
| Application | Thickness | Base and reinforcement |
|---|---|---|
| Patio, walkway, shed pad | 4" | 4-6 in compacted crushed stone, fiber mesh or 6x6 wire |
| Residential driveway, cars only | 4-5" | 6 in compacted stone, wire mesh minimum |
| Driveway with trucks, RV, dumpster | 5-6" | 6-8 in stone, #4 rebar 18 in on center |
| Garage floor | 4-5" | 6 in stone, vapor barrier, wire mesh |
| Basement floor | 3.5-4" | 4 in stone, 10 mil vapor barrier under the slab |
| Wall footing | 8 in deep x 16 in wide typical | Below frost line, 2 runs of #4 rebar |
| Deck pier or post footing | 8-12 in diameter | Below frost line, sized to the load |
Footing depth is set by local code, not preference. In northern Illinois that means 42 inches below grade to clear the frost line. Always confirm with your building department before you dig.
Reinforcement is a separate decision from thickness. Fiber mesh is mixed into the concrete at the plant for about $10 per yard and does a good job of controlling the shrinkage cracks that show up in the first month, but it adds no structural capacity. Welded wire mesh helps hold a crack tight once it forms, provided somebody actually lifts it into the middle of the slab instead of leaving it on the ground. Rebar is the only option that adds real load capacity, and it is what you want under vehicles, at slab edges, and in anything a structure sits on. On a driveway, #4 bar on 18 inch centers costs a few hundred dollars and roughly doubles the useful life of the pour.
Footings are the one place where guessing has consequences you cannot fix later. If the pour is part of an addition, a deck, or a structural change, the size comes off an approved plan. Our deck cost calculator covers pier counts and footing depth for deck framing, and load bearing wall removal gets into the footings and pads a new beam needs underneath it.
2026 Concrete Prices
Concrete pricing moved up hard between 2021 and 2024 and has been comparatively flat since. These are realistic 2026 US national numbers. Cement is heavy and cheap, so freight dominates: expect the low end near a batch plant and the high end 30 or more miles out.
| Item | 2026 price | Notes |
|---|---|---|
| Ready-mix delivered, 3000-4000 psi | $150-$185 / cu yd | Before fees, varies by market and haul distance |
| Short-load fee | $60-$80 per yard short | Applies under a 4-5 yd minimum |
| Fiber mesh, accelerator, or color | $8-$15 / cu yd each | Color for stamped work runs higher |
| Saturday or after-hours delivery | $100-$200 | Per truck |
| Extra truck time past 5-7 minutes per yard | $2-$4 per minute | Have your crew ready before it arrives |
| 40 lb bag pre-mix | $4.00-$5.00 | Yields 0.30 cu ft |
| 60 lb bag pre-mix | $5.00-$6.25 | Yields 0.45 cu ft |
| 80 lb bag pre-mix | $6.50-$8.00 | Yields 0.60 cu ft |
| Fast-setting 50 lb bag | $6.50-$9.00 | Yields 0.375 cu ft, sets in 20-40 minutes |
| Mixer rental | $60-$90 / day | Plus a deposit at most rental yards |
Big-box and supplier pricing, mid-2026. Pallet quantities of bags often carry a 5-10% discount plus delivery.
Materials are the smaller half of a finished slab. Placing and finishing labor runs $3.00-$8.00 per square foot in 2026, which is why a complete installed slab, including forms, base, rebar, concrete, and finishing, lands at $8-$18 per square foot for a broom finish. Stamped or colored decorative work is $14-$28 per square foot. Tear-out and disposal of an existing slab adds $2-$6 per square foot on top.
| Work | Cost / sq ft | 10x10 patio | 20x24 driveway |
|---|---|---|---|
| Broom finish, plain gray | $8-$18 | $800-$1,800 | $3,840-$8,640 |
| Exposed aggregate | $12-$22 | $1,200-$2,200 | $5,760-$10,560 |
| Stamped and colored | $14-$28 | $1,400-$2,800 | $6,720-$13,440 |
| Demolition of old slab | add $2-$6 | add $200-$600 | add $960-$2,880 |
Assumes reasonable site access for a truck and chute. Pumping or wheelbarrowing to a back yard adds $600-$1,200.
Common Mistakes
Ordering the exact calculated volume. Forms bow outward under the weight of wet concrete, subgrade is never perfectly flat, and a slab you formed at 4 inches will average closer to 4.5. That alone is 12% more concrete than the math says. Order 5-10% extra on ready-mix and 10% on bags. Leftover concrete becomes a splash block or a step landing. Coming up short becomes a cold joint.
Skipping base prep. The most common cause of a cracked slab is not thin concrete, it is a soft or uneven subgrade. Excavate, put down 4-6 inches of crushed stone, and compact it in lifts with a plate compactor. Concrete is strong in compression and weak in tension, so any void under the slab turns into a crack the first winter.
Pouring in the wrong weather. Above 90 degrees F, concrete can go from workable to stiff in under 30 minutes, which means you get one shot at floating it. Pour early in the morning, dampen the base and forms, and have more hands than you think you need. Below 40 degrees F, hydration slows badly, so you need an accelerator, insulated blankets, and no pour at all onto frozen ground.
Forgetting control joints. Concrete will crack. Control joints decide where. Cut or tool them within 6 to 12 hours of the pour, to a depth of one quarter of the slab thickness, spaced in feet at roughly two to three times the thickness in inches. A 4 inch slab gets joints every 8 to 12 feet.
Do not let anyone add water at the truck
Adding water to make concrete easier to place is the single fastest way to ruin it. Every extra gallon per cubic yard cuts compressive strength by roughly 150-200 psi and raises shrinkage cracking. If the mix is too stiff, the right answer is a water reducer or a plasticizer added at the plant, not a hose at the chute. The same goes for sprinkling water on the surface while finishing, which brings fines to the top and creates a weak, dusty layer that scales off in a few winters.
Underestimating placement time. A ready-mix driver typically allows 5 to 7 minutes per yard before overtime charges start. Nine yards is roughly an hour of unloading. Forms, rebar, vapor barrier, screed boards, and your entire crew all need to be in place before the truck pulls up, not while it is idling in the street.
If concrete work is one line in a larger project, the volume math is the easy part and the sequencing is not. Our basement finishing cost guide covers slab work below grade, and the tile calculator handles what goes on top once a slab has cured and you are finishing the surface.
Frequently Asked Questions
How much concrete do I need for a 10x10 slab?
A 10x10 slab poured 4 inches thick is 33.3 cubic feet, or 1.23 cubic yards. With a 10% waste factor that becomes about 36.7 cubic feet, which is 82 bags of 60 lb mix, 62 bags of 80 lb mix, or a 1.5 cubic yard ready-mix order. At 6 inches thick the same slab jumps to 1.85 cubic yards.
How many bags of concrete make a cubic yard?
A cubic yard is 27 cubic feet. Since an 80 lb bag yields about 0.60 cubic feet, a 60 lb bag about 0.45, and a 40 lb bag about 0.30, one cubic yard takes 45 bags of 80 lb, 60 bags of 60 lb, or 90 bags of 40 lb. That is roughly 3,600 lb of dry mix on a pallet and about $300-$330 in bags at 2026 prices.
How much does concrete cost per yard in 2026?
Ready-mix delivered runs $150-$185 per cubic yard in most US markets in 2026, before fees. Orders under the 4 to 5 yard minimum add a short-load fee of $60-$80 per yard short, and Saturday or after-hours delivery adds $100-$200. Fiber mesh, accelerator, and color are $8-$15 per yard each.
Is it cheaper to use bags or order ready-mix?
Bags win under about 1 cubic yard, which covers post holes, small pads, and short footings. Above 1 yard the bag price climbs past the delivered price and you are hand-mixing 45 bags or more per yard, which risks cold joints between batches. Above 2 yards, ready-mix is both cheaper and better concrete.
How thick should a concrete patio or driveway be?
Patios, walkways, and shed pads are 4 inches thick over 4 to 6 inches of compacted crushed stone. A car-only residential driveway is 4 inches minimum and 5 inches if you want it to last. Any driveway that will see a truck, an RV, or a dumpster should be 5 to 6 inches with #4 rebar on 18 inch centers.
Concrete Work in Joliet and Will County
Rehab Addicts pours patios, slabs, and footings as part of remodels and additions across Joliet, Shorewood, and Will County, IL, from a basement floor patch during a basement finishing job to new footings and flatwork on a whole-home renovation. Free estimates, and we handle the permit and frost depth details.
