How Many Bags of Concrete Do I Need? (Bag Calculator)
One cubic yard of concrete equals **45 bags of 80-lb mix**, **60 bags of 60-lb mix**, or **90 bags of 40-lb mix**. For a 10×10 patio at 4 inches thick, you need approximately **55 bags of 80-lb concrete**.
How Many Bags of Concrete Do I Need? (Bag Calculator)
One cubic yard of concrete equals 45 bags of 80-lb mix, 60 bags of 60-lb mix, or 90 bags of 40-lb mix. For a 10×10 patio at 4 inches thick, you need approximately 55 bags of 80-lb concrete.
Use the conversion tables below to find your bag count, or calculate precisely with our concrete calculator.
Bags Per Cubic Yard
Here's how many bags make one cubic yard:
| Bag Size | Yield per Bag | Bags per Cubic Yard |
|---|---|---|
| 40 lb | 0.30 cu ft | 90 bags |
| 50 lb | 0.375 cu ft | 72 bags |
| 60 lb | 0.45 cu ft | 60 bags |
| 80 lb | 0.60 cu ft | 45 bags |
Quick math: Divide 27 (cubic feet per yard) by the bag's yield to get bags per yard.
The 80-lb bags are most efficient—fewer bags to open, mix, and pour. Choose 60-lb or 40-lb bags if you have back concerns or limited lifting ability.
Quick Reference: Bags for Common Projects
Slabs and Patios (4" thick)
| Project Size | Cubic Yards | 80-lb Bags | 60-lb Bags |
|---|---|---|---|
| 4×4 ft | 0.2 | 9 | 12 |
| 6×6 ft | 0.4 | 20 | 27 |
| 8×8 ft | 0.8 | 36 | 48 |
| 10×10 ft | 1.2 | 55 | 73 |
| 12×12 ft | 1.8 | 80 | 107 |
| 10×14 ft | 1.7 | 77 | 103 |
| 12×16 ft | 2.4 | 107 | 142 |
Driveways (5" thick)
| Project Size | Cubic Yards | 80-lb Bags | 60-lb Bags |
|---|---|---|---|
| 10×18 ft | 1.4 | 63 | 83 |
| 10×20 ft | 1.5 | 70 | 93 |
| 12×20 ft | 1.9 | 83 | 111 |
| 16×20 ft | 2.5 | 111 | 148 |
Note: These include a 10% waste buffer. Round up when purchasing.
Bags for Post Holes
Post holes need surprisingly little concrete. Here's a guide:
| Hole Diameter | Hole Depth | 80-lb Bags per Hole |
|---|---|---|
| 8 inches | 24 inches | 1 bag |
| 10 inches | 30 inches | 1-2 bags |
| 10 inches | 36 inches | 2 bags |
| 12 inches | 36 inches | 2-3 bags |
| 12 inches | 42 inches | 3 bags |
For fence posts, 1-2 bags per hole is typical. Use fast-setting concrete for posts—it's designed for this application.
Use our post hole calculator for exact quantities on multiple posts.
How to Calculate Bags Yourself
Step 1: Calculate cubic feet
Length (ft) × Width (ft) × Thickness (ft) = Cubic Feet
Step 2: Divide by bag yield
Cubic Feet ÷ 0.60 (for 80-lb bags) = Number of Bags
Step 3: Add 10% for waste
Number of Bags × 1.10 = Final Bag Count
Example: 8×10 shed pad at 4" thick
- Volume: 8 × 10 × 0.33 = 26.4 cubic feet
- Bags: 26.4 ÷ 0.60 = 44 bags
- With buffer: 44 × 1.10 = 49 bags (round to 50)
For a detailed walkthrough, see how to calculate concrete.
Bag Size Comparison
Which bag size should you choose?
| Factor | 40-lb | 60-lb | 80-lb |
|---|---|---|---|
| Weight to lift | Easiest | Moderate | Heaviest |
| Bags per yard | 90 | 60 | 45 |
| Cost per cubic foot | Highest | Middle | Lowest |
| Mixing time | More batches | Moderate | Fewer batches |
Choose 80-lb bags for maximum efficiency and lowest cost per volume.
Choose 60-lb bags if 80 lbs is too heavy to lift comfortably.
Choose 40-lb bags for small projects, elderly users, or when working alone without help.
Cost Comparison by Bag Size
Bag pricing varies, but here's a typical cost-per-yard comparison:
| Bag Size | Price per Bag | Bags per Yard | Cost per Yard |
|---|---|---|---|
| 40 lb | $4.50-5.50 | 90 | ~$450 |
| 50 lb | $5.00-5.75 | 72 | ~$396 |
| 60 lb | $5.00-6.00 | 60 | ~$330 |
| 80 lb | $6.00-7.00 | 45 | ~$290 |
The 80-lb bags cost about 35% less per cubic yard than 40-lb bags. If you can handle the weight, they're the economical choice.
For full pricing context, see concrete cost per yard.
When to Use Bags vs Ready-Mix
Bags make sense for smaller projects. Here's the decision guide:
| Bag Count | Recommendation |
|---|---|
| Under 25 | Definitely bags |
| 25-45 | Bags (one person can manage) |
| 45-70 | Bags possible, consider ready-mix |
| 70-100 | Strongly consider ready-mix |
| Over 100 | Use ready-mix |
Reality check: Mixing 50 bags of 80-lb concrete takes 4-6 hours of hard labor. Mixing 100+ bags is a multi-day project. At some point, ready-mix delivery saves enough time and effort to justify the cost.
For a detailed comparison, see ready-mix vs bagged concrete.
How Many Bags Can You Mix in a Day?
Plan your project timeline realistically:
| Worker(s) | Bags per Day (Reasonable) |
|---|---|
| 1 person, by hand | 15-25 bags |
| 1 person, with mixer | 25-40 bags |
| 2 people, with mixer | 40-60 bags |
By hand means mixing in a wheelbarrow with a hoe—exhausting work.
With a mixer (rental ~$50/day) significantly increases output and consistency.
If your project needs more than 40 bags and you're working alone, plan for two days or rent a mixer.
Frequently Asked Questions
How many 80-lb bags in a cubic yard?
Approximately 45 bags of 80-lb concrete mix equal one cubic yard. Each 80-lb bag yields about 0.60 cubic feet, and one cubic yard contains 27 cubic feet.
Is it cheaper to buy bags or ready-mix?
Ready-mix costs $125-175 per yard; 80-lb bags cost ~$290 per yard. Ready-mix is cheaper per yard, but has minimum orders and delivery fees. For projects under 1 yard, bags often cost less total. Over 1.5 yards, ready-mix usually wins.
How many bags do I need for a fence post?
Most fence posts need 1-2 bags of 80-lb concrete per hole, assuming a 10-inch diameter hole that's 30-36 inches deep. For a 20-post fence, plan on 30-40 bags of fast-setting concrete.
Should I use 60-lb or 80-lb bags?
Use 80-lb bags for efficiency and cost savings—you'll mix fewer batches and spend less money. Choose 60-lb bags if 80 lbs is too heavy to lift comfortably. The 60-lb bags aren't significantly easier to mix, just lighter to carry.
Key Takeaways
- 1 cubic yard = 45 bags of 80-lb concrete
- 10×10 slab (4"): ~55 bags
- Fence post: 1-2 bags per hole
- 80-lb bags are most cost-effective
- Consider ready-mix over 70+ bags—mixing takes longer than you think
Use our concrete calculator or slab calculator for precise quantities. For more background, see how much concrete you need or browse all concrete guides.