Concrete Yardage Calculator
Cubic yards for a slab, how many ready-mix trucks that is, and the short-load fee most calculators never mention.
7.41 yd³ neat plus 8% waste
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How to work it out yourself
- 1
Work in feet, convert the thickness
Length and width are already in feet. Thickness is in inches, so divide it by 12 before multiplying. A 4 in slab is 0.333 ft; a 5 in slab is 0.417 ft. Getting this one conversion wrong is how people end up ordering three times what they need.
- 2
Multiply, then divide by 27
Length × width × thickness gives cubic feet. There are 27 cubic feet in a cubic yard, so divide by 27. Concrete is sold by the yard and nothing else — a supplier will not know what you mean if you ask for cubic feet.
- 3
Add waste before you order
Forms bow, subgrade is never perfectly level, and the last wheelbarrow always takes more than it should. Between 5% and 10% is normal; 8% is a sensible default. Running short mid-pour means a cold joint, which is a permanent weakness in the slab and a callback you cannot fix.
- 4
Divide by truck capacity for loads
A full ready-mix truck carries 8 to 10 yards, usually around 9. Anything over that is more than one truck, and two trucks need to arrive close enough together that the first pour has not begun to set.
Worked example: A 24 × 36 driveway at 5 inches
| Area | 24 × 36 = 864 sq ft |
| Thickness in feet | 5 ÷ 12 = 0.417 ft |
| Cubic feet | 864 × 0.417 = 360 cu ft |
| Cubic yards | 360 ÷ 27 = 13.3 yd³ |
| With 8% waste | 13.3 × 1.08 = 14.4 yd³ |
| Trucks | 14.4 ÷ 9 = 2 loads |
Order 14.5 yards. At roughly $160 a yard that is about $2,320 in concrete before anything else on the job.
The short-load fee
Under about 3 yards, most suppliers add a short-load charge — often $60 to $150 — because they are sending a whole truck for a partial load. It lands on the invoice after you have already quoted the job, so it comes out of your margin. Ask your supplier what their minimum is and what the penalty costs, then either price it in or add enough to the pour to clear the threshold. It is the single most common way a small slab quietly loses money. If there are steps or deck piers on the same job, adding them to the same order is usually what clears the threshold.
Turn this into a quote your client can accept
You have the quantities. What wins the job is a priced, branded estimate in your client’s hands before the other two bidders get back to them.
- First quote free — no card, no account
- Your prices and your logo, saved once
- See the moment your client opens it
Common questions
How many yards of concrete do I need for a 20 × 30 slab?
At 4 inches thick, a 20 × 30 slab needs 7.4 cubic yards of concrete, or about 8 yards once you add the usual 8% for waste. At 5 inches it is 9.3 yards, or 10 with waste. At 6 inches it is 11.1 yards, or 12 ordered.
How many cubic feet are in a yard of concrete?
27. A cubic yard is 3 ft × 3 ft × 3 ft. It is the only unit ready-mix suppliers quote in, so every calculation ends with dividing cubic feet by 27.
How much concrete does one truck hold?
A standard ready-mix truck carries 8 to 10 cubic yards, with 9 being typical. Weight limits, not drum capacity, are usually what caps it — a full load is around 40,000 lb of concrete.
How much extra concrete should I order for waste?
Between 5% and 10%. Use 5% on a small, tightly formed slab on a flat, well-prepared subgrade, and 10% where the subgrade is rough or the forms are long. Running short is far more expensive than a little left over — a cold joint is permanent.
How thick should a concrete driveway be?
Four inches is standard for cars. Go to 5 or 6 inches if trucks, RVs or a skid steer will use it, and put reinforcement in either way. The extra inch on a 24 × 36 driveway costs roughly 2.9 more yards — call it $460 in concrete — which is far less than replacing a cracked slab.
What does a yard of concrete cost?
Commonly $140 to $190 delivered in 2026, depending on region, mix and how far the truck travels, plus fees for short loads, long unloading times and Saturday pours. Your own supplier's number is the only one worth quoting from — put it in your price book and every quote uses it automatically.
Put this calculator on your own site
Free to use anywhere — a supplier’s resources page, a builder’s blog, a trade forum answer. It works on a phone, needs no account from your visitors, and we will not change it out from under you. All we ask is that you keep the credit line underneath, which is the second half of the snippet.
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