How to Estimate Concrete Yards
Calculating cubic yards is the first 30 percent. The rest is the order, the spec, and the truck.
Most articles stop the moment you have a yardage number. That is the easy part. The harder part is converting that number into an order the plant can actually deliver: choosing PSI, slump, and admixtures, knowing where the short-load fee kicks in, and being ready when the truck arrives. This guide covers all of it. For the volume math by shape, see how to calculate concrete. For the bag math, see how many bags do I need.
The Volume Math, Fast
A two-line refresher:
Volume in cubic feet / 27 = cubic yards
Inch shortcut: (L ft × W ft × D in) / 324 = cubic yards
Magic 81 for 4 in slabs: square footage / 81 = cubic yards
Round to the nearest quarter yard up, never down. For shape-specific work, the calculators do the conversions for you: slab, spread footing, strip footing, column or pier, stairs, curb and gutter.
Quick reference for slabs at the three most common thicknesses:
| Slab Size | 4 in | 5 in | 6 in |
|---|---|---|---|
| 10 x 10 | 1.23 cy | 1.54 cy | 1.85 cy |
| 12 x 16 | 2.37 cy | 2.96 cy | 3.55 cy |
| 14 x 24 (driveway) | 4.15 cy | 5.18 cy | 6.22 cy |
| 20 x 20 | 4.93 cy | 6.16 cy | 7.40 cy |
| 20 x 30 | 7.40 cy | 9.25 cy | 11.10 cy |
These figures are theoretical volumes before waste factor. See the next section for the real ordering number.
The Waste Factor, in Real Terms
The dispatcher will essentially ask, "are you giving me your finished volume or your ordered volume?" Be ready to answer.
- - 5 percent on simple flatwork with clean rectangular forms and a level subgrade.
- - 8 to 10 percent standard residential exterior pour. Most ready-mix dispatchers will quote you 10 percent if asked.
- - 10 to 15 percent on irregular shapes, sloped subgrade, hand-dug footings, or first-time pours.
That waste factor pays for: form bulge under hydrostatic pressure, subgrade variation, truck-mixer hold-back (the residual that does not fully discharge), spillage at the chute, and the 1 to 2 percent volume reduction from fresh to hardened concrete.
The honest punchline
If your math says 4.4 yards and you want a 10 percent buffer, you would theoretically order 4.84. Round up to 5.0, not down to 4.75. The reason is the cold-joint risk: if you run 0.2 yards short on a continuous slab, you have destroyed the structural continuity of the pour. A partial second delivery costs $300 or more in short-load fees plus the structural compromise. Order the extra. The leftover goes into a wheelbarrow form for a stepping stone.
Short-Load Fees and Minimum Delivery
This is the section nobody publishes. The numbers below are 2026 ranges from suppliers including Townsend Concrete, Cart-Away, and HomeGuide aggregated data. Verify locally, but the structure holds nationwide.
- Minimum delivery is typically 1 cubic yard. Some plants will deliver less but charge for the minimum.
- Short-load fees typically apply to orders under 5 to 9 yards depending on the supplier. The fee is $50 to $150 per yard short, or a flat $300 to $800 added to the ticket.
- Standard truck capacity is about 10 cubic yards. Some plants run smaller mini-mix trucks of 3 to 5 yards.
- Volumetric (mobile) mixers like Cart-Away and U-Cart charge by what they actually pour, often with no short-load fee but a higher per-yard rate. For 1 to 2 yard jobs in markets that have them, this is often the cheapest route.
- Saturday and Sunday surcharges are common: $50 to $100 added to the load.
- Pump truck rental is $700 to $1,500 for residential boom service, typically a 4 to 5 hour minimum. Worth it for backyard pours where the truck cannot reach.
- Standby time beyond the included unloading window (usually 5 minutes per yard) is $1.50 to $3 per minute.
The buying tactic that saves the most money
Combine all your concrete work into one delivery. A driveway plus walkway plus shed pad scheduled together can hit 9 yards and skip the short-load fee entirely, saving $400 to $1,000 compared to three separate calls. If you have multiple small projects, batch them.
What the Dispatcher Will Ask You
Treat this like a teardown of an actual phone call. The order matters because dispatchers move fast and respect customers who know the language.
1. Volume
"I need X.XX cubic yards." Round up to the nearest 0.25.
2. PSI
- - 2,500 to 3,000 PSI for footings and structural backfill
- - 3,000 to 3,500 PSI for sidewalks, patios, basement floors, sheds
- - 3,500 to 4,000 PSI for driveways and garage floors
- - 4,000+ PSI for shop floors, exposed slabs in freeze-thaw, anything carrying heavy equipment
When in doubt, ask the dispatcher what their default residential mix is. They know what works in your region.
3. Slump
- - 4 to 5 inch slump for slabs and most flatwork
- - 3 to 4 inch slump for footings
- - 5 to 6 inch slump for walls, columns, or pumped pours
Order at the lower end of what you want. Slump can be increased on site by adding water (with consequences, see below). It cannot be lowered.
4. Aggregate size
Default is 3/4 inch for most residential. 3/8 inch ("pea gravel") for tight reinforcement spacing or thin pours under 3 inches. Larger aggregate (1 inch or 1.5 inch) for mass pours like footings.
5. Air entrainment
If you are in a climate that freezes, the answer is yes, typically 4 to 6 percent air content. ACI and most state DOTs require it for exposed exterior concrete in freeze-thaw zones. Do not trowel-finish air-entrained concrete, it tears the surface.
6. Admixtures
In hot weather (above 85°F), ask about a retarder. In cold weather (below 50°F), ask about an accelerator (calcium chloride or non-chloride). The plant will recommend dosage.
7. Delivery time and access
Be honest about: width of access, overhead clearance (a loaded truck is about 13 ft tall and weighs 60,000 to 80,000 lb), whether the truck can back to the pour location or whether you need a wheelbarrow line or pump.
8. Washout
Every plant requires a washout area on site. It is illegal to wash to a storm drain. A wheelbarrow with a poly liner or a kiddie pool works for one truck. Mention this on the call so the driver knows you have it set up.
A model phone call:
"Hi, I'd like to schedule a delivery for Tuesday morning. I need 5.5 yards of 3,500 PSI mix at 4-inch slump, 3/4 inch aggregate, air-entrained at 5 percent. The site is 1234 Main Street. The truck can back directly to the pour from a paved driveway, no overhead obstructions. I'll have a washout area set up."
That sentence saves the dispatcher ten minutes of clarification and gets you treated like a serious customer. Most homeowners do not call this way and most dispatchers wish they did.
When the Truck Arrives
Slump check
A 4-inch slump that arrives at 7 inches is wet. Per ASTM C94, slump can vary up to 1 to 1.5 inches from ordered. Beyond that, you have grounds to reject the load. Visually: 4 inches looks like thick oatmeal that holds shape; 7 inches flows and will not hold a peak.
Adding water on site
One gallon per cubic yard adds about 1 inch of slump and reduces compressive strength by approximately 200 PSI. A 4,000 PSI mix becomes 3,500 PSI on the back of two extra gallons. Once you accept water added on site, the supplier's strength warranty no longer applies. You own the risk.
Hot weather (above 85°F)
Working time drops from about 90 minutes in spring to 60 minutes at 90°F+. Pre-wet the subgrade. Have the full crew on site before the truck arrives, not after. Book the earliest morning slot you can get.
Cold weather (below 40°F)
ACI 306 defines cold-weather concreting as more than 3 consecutive days below 40°F. Below 40°F, never pour onto frozen ground. Use blankets, heated enclosures, or accelerator admixtures. Below 25°F without protection, postpone.
The Five Most Expensive Yardage Mistakes
- Ordering exactly the calculated volume. Cold joint, second short-load fee, ruined finish.
- Forgetting the inch-to-foot conversion on depth. A 12x over-order. Catches new estimators.
- Misjudging access. Truck cannot reach, you did not pre-arrange a pump, the load goes off in the cul-de-sac and you wheelbarrow 6 yards by hand.
- Adding too much water on site to keep the mix workable, dropping strength below spec.
- Pouring at the wrong time of day in hot weather. Always book the earliest morning slot in summer.
A Worked Example, End to End
Project: a 14 x 24 ft driveway, 5 inches thick, freeze-thaw climate, sloped 6 inches over 24 ft.
Average depth: 5 inches
Volume: 14 × 24 × 0.417 = 140.1 cu ft = 5.19 cu yd
Plus 10% waste: 5.71 cu yd
Round up: order 6.0 cu yd
Spec to call in:
- - 6.0 cubic yards of 4,000 PSI mix
- - 4-inch slump
- - 3/4 inch aggregate
- - 5 percent air entrainment
- - Morning delivery in summer, mid-day in cooler weather
- - Truck access: 80 ft from street, no overhead issues, pour direct from chute
At a 2026 ready-mix average of $175 per cubic yard, the material cost is roughly $1,050. At 6 yards you are likely above the short-load threshold at most plants but verify locally. Pump truck not needed at this access.
The Bottom Line
The volume math is the easy part. The real skill in ordering ready-mix is the spec sheet and the logistics: knowing your PSI and slump, your air requirement, your access, your washout, your weather. Round up. Combine jobs to dodge the short-load fee. Have the crew on site before the truck arrives, not after.
For shape calculators, jump to the slab, footing, column, or stairs calculator. For the bag side of the decision, see how many bags do I need. For the underlying volume formulas, see how to calculate concrete.