Use this concrete bag calculator to estimate how many 40 lb, 60 lb, or 80 lb bags you need for patios, post holes, sidewalks, small slabs, and other DIY pours. Enter your total concrete volume in cubic yards or cubic feet, choose a bag size, add a waste allowance, and get a fast bag count before you buy materials. If you are still working out the total volume itself, start with our main concrete calculator and come back here to convert that volume into bags.
Quick Answer
For most residential projects under two cubic yards, bagged concrete is practical and avoids the time pressure of a full ready-mix truck. An 80-pound bag typically yields about 0.6 cubic feet of mixed concrete, which works out to roughly 45 bags per cubic yard. Smaller bag sizes yield proportionally less. Always round up, add five to ten percent for waste and spillage, and verify the actual yield printed on your specific bag.
How to Use This Bag Calculator
Follow these steps to get an accurate bag count for your project:
- Choose your unit system: Select cubic yards or cubic feet. Yards are common for larger pours; feet match typical form dimensions for small projects.
- Enter your total volume: Type the total volume of concrete you need. If you are still measuring, use the main concrete calculator first to get the volume.
- Select your bag size: Pick 40 lb, 60 lb, or 80 lb. The 80-pound size is most common for slabs and footings; 60-pound bags are easier to handle for solo work.
- Set a waste factor: The default is five to ten percent. Increase it if your subgrade is uneven, your forms are irregular, or you are new to concrete work.
- Review your results: The calculator returns the bag count, total volume, and total weight, so you can plan your purchase and recruit help for mixing and pouring.
Once you have your bag count, decide whether you will mix by hand, use a portable mixer, or rent a larger drum mixer. Mixing 40 or more bags is labor-intensive, so plan helpers and timing accordingly. For deck supports, pergola posts, or isolated bases, the Footing Calculator gives a footing-specific estimate. For common pre-built scenarios, browse our bag conversion pages.
Typical Bag Yields
Bagged concrete comes in several standard sizes. Each bag lists its yield on the packaging, but here are the typical averages:
Important: Always check the actual yield printed on the bag you purchase. High-early-strength, fiber-reinforced, or fast-setting mixes may have slightly different densities and yields.
Worked Examples
Two common scenarios where bagged concrete is the right call:
Example 1: Small Patio Slab (Cubic Feet)
Project: A 10 ft × 10 ft patio slab, 4 inches thick.
Step 1 – Convert thickness to feet: 4 ÷ 12 = 0.333 ft
Step 2 – Volume:
10 × 10 × 0.333 = 33.3 ft³
Step 3 – Add 10% waste: 33.3 × 1.10 = 36.63 ft³
Step 4 – Bags (80 lb, 0.6 ft³ each):
36.63 ÷ 0.6 = 61.05 → 62 bags
Result: Buy 62 bags of 80 lb mix (~4,960 lb total). Plan transport and recruit help for mixing and placement.
Example 2: Fence Post Footings (Cubic Yards)
Project: Eight fence posts, each in a 12-inch diameter hole, 3 feet deep.
Step 1 – Volume per hole (cylinder):
π × 0.5² × 3 = 2.36 ft³
Step 2 – Total for 8 holes: 2.36 × 8 = 18.88 ft³
Step 3 – Convert to yards: 18.88 ÷ 27 = 0.70 yd³
Step 4 – Add 5% waste: 0.70 × 1.05 = 0.735 yd³
Step 5 – Bags (80 lb, ~45 per yard):
0.735 × 45 = 33.08 → 34 bags
Result: About 34 bags. Post holes are deep and narrow, so mix in smaller batches and pour in stages to avoid premature setup.
When to Choose Bags vs Ready-Mix
Bagged concrete is usually the better choice for small pours under one to two cubic yards, tight-access sites, repairs, post holes, and DIY work you want to do at your own pace. Once you cross roughly two cubic yards, ready-mix often wins on labor, batch consistency, and total time on site — mixing dozens of bags by hand quickly becomes slow and tiring.
For a deeper comparison of cost, labor, and delivery logistics, see the dedicated section on the main concrete calculator page or read our how many bags do I need guide.
Common Bag-Estimating Mistakes
Errors specific to bagged concrete that can derail a project:
- Using a generic bag yield instead of the label: Yields vary by mix. Check the actual yield printed on the bag you are buying.
- Underestimating mixing time: Each 80 lb bag takes several minutes to mix properly. Fifty bags is hours of work — plan helpers and a realistic schedule.
- Ignoring working time: Bagged concrete starts to set in 30 to 90 minutes depending on temperature and mix. Never mix more than you can place in that window.
- Overloading a portable mixer: Drum mixers have capacity limits. Forcing too much in at once produces poor blending and stresses the motor.
- Not checking site access for bulk orders: A pallet of 50 bags weighs over 4,000 lb. Confirm your vehicle, driveway, and storage area can handle delivery before ordering in bulk.
Bag Calculator FAQ
How many 80 lb bags of concrete do I need for 1 cubic yard?
Approximately 45 bags. Each 80 lb bag yields about 0.6 cubic feet, and there are 27 cubic feet in a cubic yard (27 ÷ 0.6 ≈ 45). Always add a waste factor and verify the yield on your specific bag.
How many 60 lb bags do I need for 1 cubic yard?
About 60 bags of 60 lb mix. Each 60 lb bag yields roughly 0.45 cubic feet (27 ÷ 0.45 ≈ 60). Plan extra for waste, especially on uneven subgrades.
How many bags do I need for a 10 × 10 slab at 4 inches?
Volume is about 33.3 ft³ (10 × 10 × 0.333). With 10% waste that becomes ~36.6 ft³, which is roughly 62 bags of 80 lb, 82 bags of 60 lb, or 122 bags of 40 lb. See the worked example above for the full breakdown.
Can I mix bagged concrete in a wheelbarrow?
Yes — a wheelbarrow works well for one or two bags at a time. Use a garden hoe or mortar hoe to blend the dry mix with water thoroughly. For larger quantities, rent a portable electric or gas-powered mixer.
Is it better to use 60 lb or 80 lb bags?
The 80 lb size is more economical per cubic foot and means fewer bags to mix. The 60 lb size is easier to lift and handle, especially for solo work or anyone with physical limitations. Choose based on strength and the help you have on site.
How much does an 80 lb bag of concrete cost?
Prices vary by region and retailer, but in the U.S. an 80 lb bag of standard mix typically runs about $5 to $8. Once you cross one to two cubic yards, ready-mix delivery often becomes more economical per cubic yard. See our concrete cost per yard guide for a fuller comparison.
What is the shelf life of bagged concrete?
Unopened bags stored in a dry location typically last six months to a year. Concrete absorbs moisture from the air over time, causing partial hardening. Store bags off the ground on pallets and cover them with plastic. If a bag feels hard or lumpy, do not use it for structural work.
Can I pour bagged concrete in cold weather?
Curing slows dramatically below 50 °F and stops below freezing. If you must pour cold, use a fast-setting or cold-weather mix, keep the placed concrete warm with blankets or heaters, and avoid pouring if temperatures will drop below freezing within 24 hours.
Keep Planning Your Project
Now that you know how many bags you need, use the next tools and guides to compare project types, costs, and alternative ways to estimate concrete volume.
Compare cost, volume, and project type before you buy
If you are still deciding between bagged concrete and ready-mix, browse volume-based bag pages, compare slab and footing estimates, and review cost guidance before placing your order.
Whether you are estimating a small repair, a patio, or a set of post footings, these resources help you compare volume, cost, and labor before mixing concrete.
Disclaimer: This calculator provides estimates for planning purposes only. Actual concrete requirements may vary based on site conditions, form accuracy, material characteristics, and other factors. Always consult product labels, follow manufacturer instructions, and verify calculations before purchasing materials. For structural or critical applications, consult a licensed engineer or contractor. Concrete Yard Planner is an informational resource and assumes no liability for project outcomes.