Concrete Bags Per Cubic Yard: 40lb, 60lb & 80lb Guide
Buying the right number of concrete bags is one of the most critical planning steps for small DIY projects. Underordering means a mid-pour halt, which creates a structural cold joint where old concrete has already cured when you pour the fresh batch. Overordering wastes money on bags you cannot return once opened.
Understanding Concrete Bag Yields
| Bag Size | Yield (Cubic Feet) | Bags Per Cubic Yard | Bags Per Cubic Meter |
|---|---|---|---|
| 40 lb bag | 0.30 cu ft | ~90 bags | ~119 bags |
| 60 lb bag | 0.45 cu ft | ~60 bags | ~79 bags |
| 80 lb bag | 0.60 cu ft | ~45 bags | ~59 bags |
How to Calculate Your Total Bag Count
- Step 1 — Calculate cubic feet: Length (ft) × Width (ft) × Thickness (ft). Example: a 10×10 ft slab at 4 inches = 10 × 10 × 0.333 = 33.3 cu ft.
- Step 2 — Add 10% waste: 33.3 × 1.10 = 36.7 cu ft total.
- Step 3 — Divide by bag yield: 36.7 ÷ 0.60 = 61.2 → round up to 62 bags (for 80lb bags).
- Step 4 — Verify total cost and consider ready-mix if exceeding 2 cubic yards.
Quick Reference: Common Project Bag Counts
| Project | Dimensions | Cubic Yards | 80lb Bags Needed |
|---|---|---|---|
| Fence post hole | 10" dia × 24" deep | 0.04 yd³ | 2 bags |
| Mailbox base | 12" × 12" × 12" deep | 0.05 yd³ | 3 bags |
| Small walkway | 3 × 10 ft × 4" deep | 0.37 yd³ | 17 bags |
| Garden shed slab | 10 × 10 ft × 4" deep | 1.23 yd³ | 56 bags |
| Single car parking pad | 10 × 20 ft × 4" deep | 2.47 yd³ | 111 bags |
| Two-car driveway | 20 × 20 ft × 4" deep | 4.94 yd³ | 222 bags (use ready-mix) |
When to Order Ready-Mix Concrete Instead
- Labor: Mixing 90 bags of 80lb concrete by hand or with a portable mixer takes several hours and risks premature curing.
- Cost: Ready-mix per cubic yard is typically cheaper than equivalent bag quantities once labor is factored.
- Consistency: Ready-mix plants maintain precise water-cement ratios for uniform strength (typically 3,000–4,000 PSI).
- Time: A ready-mix truck delivers in one pour, preventing cold joint weaknesses between successive bag batches.
Tips for Mixing Bag Concrete Correctly
- Use a mechanical paddle mixer or rented drum mixer for anything over 5 bags to ensure proper consistency.
- Always add water gradually — too much water weakens concrete dramatically. The mix should look like thick peanut butter.
- Work in shaded conditions or early morning in summer — heat accelerates curing and limits your working window.
- Cure freshly poured concrete by misting it with water twice a day for 3–7 days to prevent surface cracking.
- Never pour concrete when ground temperature is below 40°F (4°C) without using cold-weather admixtures.
⚠️ Safety Warning: Concrete mix is caustic and can cause chemical burns on skin and eyes. Always wear waterproof gloves, safety glasses, and avoid breathing dry concrete dust. Wash any skin contact immediately with large amounts of water.
Frequently Asked Questions
How many 80lb bags of concrete equal one cubic yard?
It takes approximately 45 bags of 80lb premix concrete to equal one cubic yard (27 cubic feet) of poured concrete. Always purchase at least 10% extra to account for spills, waste, and minor measurement errors.
How many 60lb bags of concrete make a cubic yard?
You will need approximately 60 bags of 60lb premix concrete to fill one cubic yard. These smaller bags are easier to handle solo but less economical in bulk.
How many 40lb bags of concrete per cubic yard?
It takes approximately 90 bags of 40lb premix to equal one cubic yard. The 40lb bag is best for very small repair tasks such as patching steps or setting mailbox posts.
Which bag size is most cost-effective?
The 80lb bag offers the best cost-per-cubic-foot value. For jobs exceeding 1 cubic yard, consider ordering ready-mix concrete delivery instead, as bag concrete becomes extremely labor-intensive.
What is the yield of a standard concrete bag in cubic feet?
An 80lb bag yields approximately 0.60 cubic feet. A 60lb bag yields about 0.45 cubic feet. A 40lb bag yields about 0.30 cubic feet of mixed concrete.