Ready Mix Concrete Calculator
The number you give the batch plant needs two things the raw volume lacks: a waste allowance and quarter-yard rounding. This ready mix concrete calculator applies both — enter the pour, read the order.
Order from the plant
3.5 yd³
exact need 2.96 yd³ + 10%
Estimated cost
$578
at the price above
Too small for a truck?
147 bags
80-lb equivalent
Batch plants sell in quarter-yard increments, and most charge short-load fees under about 3–4 yd³ — ask before you book.
Formula
From pour dimensions to the phone number:
exact yd³ = [L (ft) × W (ft) × T (in) ÷ 12] ÷ 27 order yd³ = round up to 0.25 → exact yd³ × 1.10
The 10% covers subgrade unevenness, form losses and what stays in the drum. On unusual ground, more allowance is cheaper than a cold joint waiting on a second truck.
Example
- Slab 12 × 20 ft, 4 in. thick: 80 ft³ = 2.96 yd³ exact.
- With 10%: 2.96 × 1.10 = 3.26 yd³.
- Quarter-yard rounding: order 3.5 yd³.
- At $165 per yard: 3.5 × 165 = $578 — worth confirming the quote includes the short-load fee at this size.
Frequently Asked Questions
How much ready-mix should I order?
The exact pour volume plus about 10% for uneven subgrade and losses, rounded up to the nearest quarter yard. A 12 × 20 ft slab at 4 inches needs 2.96 yd³ — order 3.5, not 3.
Why round up to quarter yards?
Batch plants meter concrete in quarter-yard steps, and the mixer drum can't measure finer. Asking for 3.3 yards gets you either a puzzled pause or an arbitrary round — quote 3.5 and the ticket matches the pour.
What is a short-load fee?
A surcharge for small truck loads, typically under 3–4 cubic yards — often $40–$75, sometimes more. On a 1-yard job it can double the price, which is exactly when bagged mix becomes the better buy.
How long do I have to work the truck?
Plan on discharging within about an hour of batching and finishing quickly after — concrete doesn't wait. Have the crew, tools and help staged before the truck rolls; most suppliers charge for stand-by time past 5–10 minutes per yard.