You need
- 36.7cu ft
- 82bags of 60 lb
- 123bags of 40 lb
Prices: what stores and ready-mix plants post, October 2026.
- You need 1.36 cubic yards of concrete. That is 36.7 cu ft, with 10% extra for waste.
- In bags: 62 bags of 80 lb, or 82 of 60 lb, or 123 of 40 lb.
- 80 lb bags cost about $403 to $689.
- Ready-mix costs about $175 to $205, plus the truck fee.
- With a $300 truck fee (an example), ready-mix costs less above about 1.3 cubic yards. Your job is bigger than that.
- That is 2.5 tons of bags to lift and mix by hand.
Text this to a ready-mix plant
Hi! I need about 1.36 cubic yards of 3000 psi concrete, delivered. What would it cost, with the truck and short-load fees?
Bags for a 4 inch slab
Bags of concrete mix for a slab 4 inches10 cm thick, with 10% extra.
| Slab | Cubic yardsCubic meters | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 4 × 4 ft1.2 × 1.2 m | 0.220.17 | 10 | 14 | 20 |
| 6 × 6 ft1.8 × 1.8 m | 0.490.37 | 22 | 30 | 44 |
| 8 × 8 ft2.4 × 2.4 m | 0.870.66 | 40 | 53 | 79 |
| 10 × 10 ft3.0 × 3.0 m | 1.361.04 | 62 | 82 | 123 |
| 10 × 12 ft3.0 × 3.7 m | 1.631.25 | 74 | 98 | 147 |
| 12 × 12 ft3.7 × 3.7 m | 1.961.50 | 88 | 118 | 176 |
| 12 × 20 ft3.7 × 6.1 m | 3.262.49 | 147 | 196 | 294 |
| 20 × 20 ft6.1 × 6.1 m | 5.434.15 | 245 | 326 | 489 |
Bag yields: Quikrete Concrete Mix and Sakrete High-Strength data sheets. An 80 lb bag makes 0.60 cu ft. A 60 lb bag makes 0.45. A 40 lb bag makes 0.30.
Bags or ready-mix?
A bag is cheap, but you need a lot of them. Ready-mix costs less per yard, but the truck has a fee.
- Bagsabout $292 to $500 a cu yd$382 to $654 a m³45 bags of 80 lb make one cubic yard. An 80 lb bag costs $6.49 to $11.12.
- Ready-mixabout $129 to $151 a cu yd$169 to $198 a m³Plus a truck fee, and more for a small load. The two plants we found that post a truck fee charge $305 and $364.
At typical prices, each cubic yard costs about $237 more in bags. So a $300 truck fee pays for itself above about 1.3 cubic yards1.0 m³. That is about 57 bags of 80 lb. Type your plant's fee in the calculator to see your own number.
How the math works
- Area. Length times width. For a circle, half the width times itself, times 3.1416. One meter is 3.28084 feet.
- Cubic feet. Area in sq ft times thickness in inches, divided by 12. Then times how many, and plus the extra for waste. Divided by 27 gives cubic yards.
- Extra. NRMCA, the ready-mix trade group, says add 4 to 10% for waste. Sakrete says add 10%. We start at 10%.
- Bags. Cubic feet divided by what one bag makes: 0.60 cu ft for 80 lb, 0.45 for 60 lb, 0.30 for 40 lb (Quikrete and Sakrete). Rounded up.
- Prices. What stores post for bags, as dollars per cubic foot of concrete: the middle 80% runs $10.82 to $18.53. What ready-mix plants post a cubic yard: $129 to $151. Too few plants post truck fees for a range, so you type yours.
- Bags or ready-mix. The truck fee, divided by how much more a cubic yard of bags costs than ready-mix, at typical prices.
Questions
How many bags of concrete do I need?
Find the cubic feet, then divide by what one bag makes. An 80 lb bag makes 0.60 cu ft, so a cubic yard is 45 bags. A 60 lb bag makes 0.45 cu ft (60 a yard). A 40 lb bag makes 0.30 cu ft (90 a yard).
How much concrete do I need for a slab?
Length × width in feet × thickness in inches ÷ 12 = cubic feet. A 10 × 10 ft slab, 4 in thick, is 33.3 cu ft, or 1.23 cubic yards. With 10% extra, buy 62 bags of 80 lb.
How many bags of concrete for a fence post?
A hole 10 in across and 2 ft deep holds 1.09 cu ft. A 4 × 4 post takes 0.17 of that. So you need about 0.92 cu ft: 2 bags of 80 lb, or 3 of 60 lb. Fast-setting mix makes less per bag, so check its bag.
When is ready-mix cheaper than bags?
With a truck fee near $300, ready-mix costs less above about 1.3 cubic yards. Below that, bags win. Type your plant's fee in the calculator to see your number.
How much extra concrete should I order?
NRMCA says 4 to 10% more for waste and uneven ground. Sakrete says 10%. Running short in the middle of a pour is worse than a few bags left over.
Sources
- Quikrete Concrete Mix #1101 data sheetOct 2022What 40, 60 and 80 lb bags make
- Sakrete High-Strength Concrete Mix data sheetJan 2024The same yields; add 10%
- NRMCA, Concrete in Practice 82016Add 4 to 10% for waste