Concrete Cost Calculator
With 10% waste, this 12 ft by 20 ft by 4 in pad is 3.26 cubic yards. The example price of $135 per cubic yard makes the concrete line $440.00. That $135 is sitting in the box so the total can be checked. Replace it with the quote you were given.
Last updated . Waste starts at 10%, a planning allowance you can change. The ready-mix box starts at 135 only because it is labeled as an example. The bag price, delivery fee, and labor rate start empty.
A concrete cost calculator for a slab or a pad. Volume comes from the dimensions plus the waste percent you type. The price is the ready-mix price per cubic yard you type, or a bag price. An optional delivery or short-load fee and labor per square foot are added only when you fill them in.
Bag counts and the 0.60, 0.45, and 0.30 cubic-foot yields: concrete bag calculator. Volume and weight without a price: concrete slab calculator. Comparing a sack pour with a truck: bags versus ready-mix.
Slab or pad cost
135 is an example so the total can be checked. Replace it with your quote. It is not a local price.
Waste is added to the volume before the price or the bag count. 10% is a planning allowance you can change, not a code rule. Labor uses the slab area, not the wasted volume. Bag yields match the bag calculator: 0.60, 0.45, and 0.30 cubic feet. The count rounds up. Empty price boxes are not a market price.
Results
How the concrete cost is calculated
Net volume = length × width × thickness. Order volume = net volume × (1 + waste ÷ 100). The default 12 ft × 20 ft × 4 in is 80 cubic feet, which is 80 ÷ 27 cubic yards and displays as 2.96. Ten percent waste makes the order 88 cubic feet, which displays as 3.26 cubic yards. The area is 240.00 square feet.
Ready-mix concrete = order cubic yards × the price you type, using the full yards, not the rounded 3.26. (88 ÷ 27) × 135 = 440.00. The displayed 3.26 × 135 is 440.10, and that figure is not used. The 135 in the price box is an example so this check can be made. Replace it with the plant’s quote. Delivery and labor start empty and count as zero until you type them. Labor = slab area × your rate per square foot. It does not charge for the wasted volume.
Bag mode uses the yields already stated on the bag calculator: an 80 lb bag is 0.60 cubic feet, a 60 lb bag is 0.45 cubic feet, and a 40 lb bag is 0.30 cubic feet. Bags = order cubic feet ÷ yield, rounded up. At 10% waste that is 147, 196, and 294 bags. The bag price box starts empty. Type the price on the bag you are buying. An empty price leaves the dollar lines as “Enter a price” and still shows the volume.
Example totals for this slab
The dollar rows use 135 per cubic yard or 6 per bag only as numbers sitting in the boxes. They are not market prices.
| Case | Order | Bags | Concrete | Total |
|---|---|---|---|---|
| 10% waste, example $135/yd³ | 3.26 yd³ · 88.00 ft³ | — | $440.00 | $440.00 |
| 0% waste, example $135/yd³ | 2.96 yd³ · 80.00 ft³ | — | $400.00 | $400.00 |
| 10% waste, 80 lb, typed $6 | 3.26 yd³ · 88.00 ft³ | 147 | $882.00 | $882.00 |
| 10% waste, 60 lb, typed $6 | 3.26 yd³ · 88.00 ft³ | 196 | $1,176.00 | $1,176.00 |
| 10% waste, 40 lb, typed $6 | 3.26 yd³ · 88.00 ft³ | 294 | $1,764.00 | $1,764.00 |
| $135/yd³, $75 delivery, $2/ft² labor | 3.26 yd³ · 88.00 ft³ | — | $440.00 | $995.00 |
Worked example
Leave 12 ft by 20 ft by 4 in, waste at 10, and the example price at 135. With waste reads 3.26 yd³ · 88.00 ft³. Concrete reads $440.00. Total reads $440.00. Replace 135 before you treat the total as your job.
Concrete cost questions
What does a 12 by 20 foot slab, 4 inches thick, cost at $135 a yard?
Leave length at 12 ft, width at 20 ft, thickness at 4 in, and waste at 10. Leave the price mode on Per cubic yard. The price box starts at 135, and the note under it says that 135 is an example, not a local price. Area reads 240.00 ft². Net volume reads 2.96 yd³ · 80.00 ft³. With waste reads 3.26 yd³ · 88.00 ft³. Concrete reads $440.00. Delivery reads $0.00. Labor reads $0.00. Total reads $440.00. The $440.00 is the example price times the order volume. It is not a quote.
Why is the total $440.00 and not $440.10?
The yard line rounds 88 ÷ 27 to 3.26. The dollar line uses the full 88 ÷ 27 cubic yards. (88 ÷ 27) × 135 = 440 exactly. 3.26 × 135 = 440.10, and that is not the total on the panel.
What is the same slab with no waste?
Set waste to 0 and leave the example price at 135. Net volume and With waste both read 2.96 yd³ · 80.00 ft³. Concrete reads $400.00. Total reads $400.00. (80 ÷ 27) × 135 = 400 exactly. The displayed 2.96 × 135 would be 399.60, which is not the line used. Ten percent is a planning allowance you can change. It is not a code rule.
How many 80 lb bags, and what if a bag is $6?
Set the price mode to Per bag and leave the bag on 80 lb — 0.60 ft³. Waste stays at 10. Bags reads 147. The bag price box starts empty. Type 6. Concrete reads $882.00 and Total reads $882.00. 147 × 6 = 882. The $6 is a number you typed so the line can be checked. It is not a store price. The count is the order volume divided by 0.60 cubic feet, rounded up. At 0% waste the same bag reads 134.
How many 60 lb and 40 lb bags is that pour?
Stay on Per bag with waste at 10. Choose 60 lb — 0.45 ft³ and Bags reads 196. Choose 40 lb — 0.30 ft³ and Bags reads 294. Those yields are the figures already stated on the concrete bag calculator: 0.60, 0.45, and half of 0.60. The count rounds up. If the bag price is still 6, the concrete line reads $1,176.00 at 196 bags and $1,764.00 at 294 bags.
How do a delivery fee and labor get added?
Switch back to Per cubic yard and leave the example price at 135 and waste at 10. Type 75 in Delivery or short-load fee and 2 in Labor per square foot. Concrete stays $440.00. Delivery reads $75.00. Labor reads $480.00. Total reads $995.00. Labor is the slab area, 240 square feet, times the rate you type. It does not add the wasted volume. 440 + 75 + 480 = 995. Both fees are amounts you type. Empty boxes count as zero.
What if I clear the price?
Clear the price per cubic yard so the box is empty. Area, net volume, and the waste volume still show. Concrete reads Enter a price. Total reads Enter a price. An empty price is not treated as a market price. Volume for this slab, without a dollar line, is the concrete slab calculator. Bag counts without a price are the concrete bag calculator.