80 Lb Sakrete Calculator
An 80-pound bag of Sakrete High-Strength Concrete Mix yields about 0.60 cubic feet of finished concrete. That single number is the key to the whole project: divide your slab’s total cubic feet by 0.60 and you have your bag count. A 10 ft by 10 ft patio poured 4 inches thick needs roughly 33 cubic feet, which works out to 56 bags before waste.
The 80 Lb Sakrete Calculator below does that math for you with the details most bag charts skip. It handles slabs, post holes, round columns, and footings, adds a waste factor for spillage and uneven ground, and estimates your material cost and the water you will need. The 80-pound bag is the sweet spot for serious DIY work: big enough that a patio doesn’t take forever, small enough that one person can still lift and mix it.
Quick Answer
Key takeaways
- 80-lb Sakrete bag = 0.60 cu ft. 60-lb = 0.45 cu ft. 40-lb = 0.30 cu ft.
- Always add 5–10% waste for spillage, uneven excavation, and concrete left in the wheelbarrow.
- 45 bags of 80-lb mix make one cubic yard. Above a yard, price delivered ready-mix before buying bags.
- Figure about 3.5 quarts of water per 80-lb bag, added gradually. You can add water, never take it away.
- Quick Answer
- Where the 0.60 cubic feet per bag comes from
- The bag-count formulas the calculator uses
- Worked example, checked against this exact tool
- Bag size cheat sheet for Sakrete concrete
- When bags stop making sense: the ready-mix cutoff
- Mixing and water: what the bag label actually means
- What competing bag calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
- References
Where the 0.60 cubic feet per bag comes from
A bag of concrete is not a bag of volume, it is a bag of dry ingredients: cement, sand, and coarse aggregate in a fixed ratio. When you add water, the mixture packs down, so the finished volume is less than the dry volume in the bag. Sakrete’s published technical data lists the finished yields: an 80-lb bag of High-Strength Concrete Mix makes about 0.60 cubic feet, a 60-lb bag makes 0.45, and a 40-lb bag makes 0.30. Quikrete publishes the same 0.60 figure for its 80-lb bag, so this is an industry figure, not a brand quirk.
Field yield moves a little with how much water you use and how the concrete is placed, which is exactly why the waste factor exists. The calculator above uses 0.60 as the base and lets you pad it. If you are pouring on a hot, windy day or over rough subgrade, use the 15% setting. You will not regret the extra bags; you will regret the cold joint where a second batch met the first.
The bag-count formulas the calculator uses
Every shape reduces to the same two steps: find the volume in cubic feet, then divide by 0.60 and round up.
Volume of a slab or strip footing. Length (ft) × width (ft) × thickness (in) ÷ 12. All in one line: a 12×8 ft walkway at 4 in thick is 12 × 8 × 4/12 = 32 cubic feet.
Volume of a round hole or column. π × (diameter in feet ÷ 2)² × depth in feet. An 8-inch post hole 3 feet deep is π × (0.333)² × 3 ≈ 1.05 cubic feet.
Bags = volume ÷ 0.60, then round up. 32 cubic feet ÷ 0.60 = 53.3, so 54 bags. Then multiply by 1 + waste factor: 54 × 1.10 ≈ 60 bags with 10% waste. Note the calculator rounds once, at the very end.
Worked example, checked against this exact tool
Enter the pre-filled defaults (10×10 ft slab, 4 in thick, 10% waste, $5.50 per bag) and click Calculate. Here is what the tool returns, verified against the underlying code:
| Figure | Value |
|---|---|
| Concrete volume | 33.33 cu ft (1.23 cubic yards) |
| Exact bags (0.60 yield) | 55.56 |
| Bags with 10% waste | 61.11 → 62 bags |
| Water needed | ≈ 54.3 gallons (3.5 quarts per bag) |
| Estimated material cost | $341.00 |
Try the fence-post defaults: switch the shape to post hole, keep 10-inch diameter, 36-inch depth, 8 holes. The tool gives about 1.05 cubic feet per hole, 8.4 cubic feet total, which is exactly 14 bags at 0.60 yield, or 16 with 10% waste. That matches Sakrete’s own guidance that a single 80-lb bag fills roughly three standard 10×36 post holes.
Bag size cheat sheet for Sakrete concrete
The 80-pound bag is not the only option, and for small jobs it is the wrong one. Here are Sakrete’s published yields so you can compare before you shop:
| Bag size | Yield (cu ft) | Bags per cubic yard | Best for |
|---|---|---|---|
| 40 lb | 0.30 | 90 | Repairs, single post holes |
| 60 lb | 0.45 | 60 | Medium jobs, easier lifting |
| 80 lb | 0.60 | 45 | Slabs, patios, sidewalks |
| 90 lb | 0.66 | 41 | Pro pours, fewer bags to handle |
The 60-lb bag is worth a look if you are working alone all day: 60 bags of the 60-pounder versus 45 of the 80-pounder for the same yard, but each lift is 20 pounds lighter. If the slab is a foundation for a deck, run the lumber and labor numbers through a deck cost calculator to see the full project picture before you buy concrete.
When bags stop making sense: the ready-mix cutoff
Bagged concrete is convenient, not cheap. At big-box prices an 80-lb bag typically runs $5 to $7, which puts a cubic yard at $225 to $315 in bags alone, before your labor and the water. A ready-mix truck delivers that same yard for roughly $130 to $150 in most markets, mixed consistently and placed in minutes instead of the hours you will spend on 45 wheelbarrow loads.
The practical cutoff is about one cubic yard (27 cubic feet, 45 bags). Under it, bags win on convenience: no minimum-load fees, no scheduling, no truck tearing up the lawn. Over it, call the plant. The calculator flags this for you automatically: when your volume crosses a yard, the note under the result suggests pricing ready-mix before buying. For a driveway-sized project the difference can be several hundred dollars.
Mixing and water: what the bag label actually means
Sakrete’s labeling calls for about 3.5 quarts of water per 80-lb bag. That figure is a starting point, not a target: humidity, the moisture already in the aggregate, and air temperature all move it. Add the water gradually and mix to a workable consistency, thick enough to hold its shape on a trowel. Every extra quart past that point lowers the final strength, and there is no way to take water back out.
Hand-mixing one 80-lb bag in a wheelbarrow takes 5 to 8 minutes of real work. A portable electric mixer handles two bags in 3 to 4 minutes. For the 62-bag patio in the worked example, expect a full day of mixing for two people, which is another reason the ready-mix cutoff exists. High-Strength Concrete Mix reaches foot traffic in about 24 hours and vehicle traffic in about 72, per Sakrete’s published data, with full 4,000 PSI strength at 28 days. Keep the surface damp for the first week and do not schedule heavy loads before that 28-day mark.
What competing bag calculators miss
We checked the top-ranking bag calculators before writing this page. They get the 0.60 yield right, but the pattern of gaps is consistent.
No waste factor. Most calculators divide by the yield and round up, then stop. Real pours lose concrete to spillage, over-dug edges, and the half bag stuck in the wheelbarrow. A chart that says 56 bags for a 33-cubic-foot patio is setting you up for a store run mid-pour. The waste toggle here is the difference between a plan and a guess.
Slab-only math. Several popular calculators only accept length, width, and thickness. Fence posts, deck footings, and sonotube columns are round, and a round hole 10 inches wide and 3 feet deep is not a shape you can fake with rectangle math. The shape selector covers the actual projects people pour.
No cost or water estimate. Knowing you need 62 bags is half the shopping trip. The water estimate (about 54 gallons for the worked example) tells you whether the garden hose reaches, and the cost row tells you whether bags or ready-mix win before you are standing in the aisle.
Generic yields presented as exact. A few calculators show bag counts to two decimal places with no rounding, or bury the yield figure so you cannot check it. This page states the 0.60 figure up front and shows the unrounded exact count alongside the rounded-up buy count, so the math is auditable.
Frequently asked questions
A 10×10 ft slab at 4 inches thick is 33.3 cubic feet. At 0.60 cubic feet per 80-lb bag that is 55.6 bags, rounded up to 56. With a standard 10% waste factor, buy 62 bags. The calculator above runs this exact scenario with its default settings.
About 45. One cubic yard is 27 cubic feet, and 27 ÷ 0.60 = 45. This is why bagged concrete stops making sense around a yard: 45 bags at $5 to $7 each costs $225 to $315, while a ready-mix truck delivers the same yard for roughly $130 to $150.
About 3.5 quarts per 80-lb bag, per Sakrete’s labeling. Add it gradually and mix to a workable consistency. Too much water weakens the concrete and cannot be removed, so start dry and add slowly.
A 10-inch diameter hole 3 feet deep is about 1.05 cubic feet, so one 80-lb bag (0.60 cu ft) is not quite enough; two bags cover it with margin. Per Sakrete’s guidance, one 80-lb bag fills roughly three shallower 10×24-inch post holes. Use the post-hole shape in the calculator for your exact depth.
For standard concrete mix, very little: both publish 0.60 cubic feet of yield per 80-lb bag and 4,000 PSI strength at 28 days. Sakrete often runs $0.50 to $1.00 cheaper per bag at big-box stores, while Quikrete has wider distribution and more specialty products. For a plain slab, buy whichever is in stock.
Yes, but it is real work. Hand-mixing one 80-lb bag in a wheelbarrow takes 5 to 8 minutes, and a 60-bag patio is a full day for two people. A portable electric mixer roughly doubles your pace. If you are working solo all day, consider 60-lb bags: more bags, but each lift is 20 pounds lighter.
Four inches is the standard for patios, walkways, and shed floors. Driveways and anything carrying vehicles need 5 to 6 inches, and Sakrete High-Strength Concrete Mix is rated for applications 2 inches and thicker. Thinner work calls for Sakrete Sand Mix, not the standard concrete mix.
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References
- Sakrete technical data via Outdoor Warehouse Supply, “Sakrete Concrete” – bag yields (80 lb = 0.60 cu ft, 60 lb = 0.45, 40 lb = 0.30), 4,000 PSI strength, 24-hour foot traffic and 72-hour vehicle traffic guidance. Sakrete Concrete Product Data. Accessed October 19, 2026.
- vCalc, “Concrete to Water Ratio” – derives 3.5 quarts of water per 80-lb Sakrete bag from the product labeling. vCalc: Concrete to Water Ratio. Accessed October 19, 2026.
- Concrete Calculator Yards, “Concrete Calculator, Cubic Yards, Bags and Cost (2026)” – ACI-based methodology, 10% waste factor as industry standard, 45-bag-per-yard figure, ready-mix pricing benchmarks. Concrete Calculator Yards Methodology. Accessed October 19, 2026.
- Woodworking Advisor, “Concrete Calculator, Estimate Bags, Yards and Cost” – bag-yield figures from Quikrete and Sakrete, ready-mix vs bags cutoff guidance, 5-10% waste buffer. Woodworking Advisor Concrete Calculator. Accessed October 19, 2026.
- Civilsir, “How Many 80lb Bags of Concrete Make a Yard” – derivation of the 45-bags-per-yard figure (27 cu ft / 0.60 cu ft). Civilsir: 80lb Bags per Yard. Accessed October 19, 2026.