Typical: 4" patio, 6" driveway, 8" structural
Consider ready-mix concrete
Your project needs 1.36 cubic yards. At 1+ yd3, ordering ready-mix from a truck is usually faster, cheaper per yard, and produces a stronger, more consistent mix than bagged concrete.
Always buy 1-2 extra bags. Yields and prices are approximate (updated July 2026) - verify with your supplier.
Prices are estimates only and vary by region and retailer.
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Yields are approximate - verify bag counts with your local supplier before purchasing.
Concrete Bags by Common Project (Quick Reference)
Estimates include 10% waste factor. Always buy 1-2 extra bags. Use the calculator above for your exact dimensions.
| Project | Dimensions | Cu Ft | 60 lb Bags | 80 lb Bags |
|---|---|---|---|---|
| Small Patio Slab | 8x8 ft, 4" thick | 18.1 | 41 | 31 |
| Standard Patio | 10x10 ft, 4" thick | 28.2 | 63 | 47 |
| Large Patio | 12x12 ft, 4" thick | 40.6 | 91 | 68 |
| Garage Floor | 20x20 ft, 4" thick | 162.7 | 362 | 272 |
| Sidewalk Section | 4x8 ft, 4" thick | 9.7 | 22 | 17 |
| Deck Footing (x1) | 12" dia, 42" deep | 2.6 | 6 | 5 |
| Fence Post (x1) | 10" dia, 30" deep | 1.0 | 3 | 2 |
| Fence Post (x6) | 10" dia, 30" deep | 6.1 | 14 | 11 |
| Mailbox Post | 8" dia, 24" deep | 0.5 | 2 | 1 |
| Strip Footing | 20 ft x 12" wide x 12" deep | 22.0 | 49 | 37 |
Concrete Bag Size Comparison
All bag sizes produce the same strength concrete. Choose based on your budget, physical ability, and project size.
| Bag Size | Yield (cu ft) | Price (USD est.) | Cost per cu ft | Best For |
|---|---|---|---|---|
| 25 lb | 0.20 cu ft | ~$5.50 | ~$27.50 | Small repairs, single post holes |
| 40 lb | 0.30 cu ft | ~$6.98 | ~$23.27 | Small projects, easy handling |
| 60 lb | 0.45 cu ft | ~$9.48 | ~$21.07 | Medium projects, good balance |
| 80 lb | 0.60 cu ft | ~$11.98 | ~$19.97 | Best value, larger projects |
| 20 kg (metric) | 0.0085 m3 | ~$8.97 CAD | varies | Canadian metric projects |
| 30 kg (metric) | 0.0128 m3 | ~$12.97 CAD | varies | Larger Canadian projects |
When to Use Ready-Mix vs Bagged Concrete
Bagged concrete is convenient for small projects. Ready-mix is more economical and produces better results for larger pours.
| Volume | Recommendation | Reason |
|---|---|---|
| Under 0.5 cu yd | Bagged concrete | Easy, no minimum order, mix as needed |
| 0.5 - 1.0 cu yd | Bagged concrete | Still manageable, avoids truck minimum charges |
| 1.0 - 3.0 cu yd | Ready-mix or short-load | Ready-mix cheaper per yard, better consistency |
| Over 3.0 cu yd | Ready-mix truck | Significantly cheaper, faster, stronger result |
Metric Bags: 20 kg and 30 kg
Canadian and UK bags are sold by the kilogram, not the pound, and the yields do not line up neatly with US sizes. These are the numbers most people are looking for when they ask how many bags fit in a cubic yard or a cubic metre.
| Bag | Yield | Bags per m³ | Bags per cu yd | Bags per cu ft |
|---|---|---|---|---|
| 20 kg | 0.0085 m³ (0.30 cu ft) | 118 | 90 | 3.3 |
| 30 kg | 0.0128 m³ (0.45 cu ft) | 78 | 60 | 2.2 |
| 40 kg | 0.0170 m³ (0.60 cu ft) | 59 | 45 | 1.7 |
Round up. A cubic yard needs 60 x 30 kg bags or 90 x 20 kg bags, and at that point a ready-mix truck is cheaper and far less work — see the comparison below.
Frequently Asked Questions
How many 80 lb bags of concrete do I need for a 10x10 slab?
A 10x10 ft slab at 4 inches thick requires approximately 47 bags of 80 lb concrete mix (28.2 cubic feet including 10% waste). At 6 inches thick you would need approximately 70 bags. Always buy 1-2 extra bags to account for spillage and uneven subgrade.
What size concrete bag gives the best value?
80 lb bags offer the lowest cost per cubic foot at roughly $19.97, compared to $27.50 for 25 lb bags. However, an 80 lb bag is heavy to handle repeatedly. For projects under 10 bags the handling difference matters more than the savings.
When should I use ready-mix concrete instead of bags?
Above roughly 1 cubic yard, ready-mix becomes cheaper per yard and produces more consistent results. Below 0.5 cubic yards, bagged concrete avoids truck minimum charges and lets you mix at your own pace.
How deep should a concrete slab be?
Four inches is standard for patios, walkways and shed floors. Six inches is used for driveways and anywhere vehicles park. Adding two inches to a slab increases your concrete volume by 50 percent, so confirm the thickness before ordering.
How much concrete do I need for a post hole?
A 10 inch diameter hole 30 inches deep takes about 1.0 cubic foot, which is 3 bags of 60 lb or 2 bags of 80 lb mix. Multiply by your post count and add one spare bag - post holes are rarely as uniform as planned.
Prices are estimates only and vary by region. Verify bag counts with your local supplier before purchasing.