How Many Bags of Concrete Do I Need? 60-lb vs 80-lb Bag Count by Project (2026 Speed Reference)
One 80-lb bag yields 0.60 ft³; one 60-lb bag yields 0.45 ft³; one 40-lb bag yields 0.30 ft³ of cured concrete (Quikrete + Sakrete yield charts, verified to ASTM C387). That's 45 bags of 80-lb or 60 bags of 60-lb per cubic yard. This guide gives you the exact bag count for every common project — fence posts, deck footings, patio pads, sidewalk sections, slab pours — with the 80-lb vs 60-lb cost-per-cubic-foot breakdown that home centers won't show you on the shelf tag.
Walk into any home center on a Saturday morning and you'll see four pallets of concrete bags — 40-lb, 60-lb, 80-lb and "high early strength" 80-lb — and zero information on which one solves your problem. The right number isn't on the bag. It's a function of your cured volume (what your pour needs to hold), the bag yield (a fixed number per ASTM C387), and the cost-per-cubic-foot that the bag-price-only label deliberately hides.
This guide gives you the three answers most home-center signage skips: how many bags for your specific project, which bag size to buy when you're between options, and when bagged stops making sense and you should call a ready-mix truck instead (spoiler: it's somewhere between 1.0 and 1.5 cubic yards, not the 2 yd³ most articles claim).
Bag Yields: The Three Numbers That Decide Everything
The bag-to-volume conversion is fixed by ASTM C387 (premix consistency standard) and manufacturer testing. Memorize these three numbers and you can answer every "how many bags" question in under a minute:
- 40-lb bag = 0.30 ft³ cured (≈ 90 bags per cubic yard, 27 ft³ / 0.30)
- 60-lb bag = 0.45 ft³ cured (≈ 60 bags per cubic yard, 27 / 0.45)
- 80-lb bag = 0.60 ft³ cured (≈ 45 bags per cubic yard, 27 / 0.60)
Notice the yield isn't linear with bag weight — a 60-lb bag is 75% the weight of an 80-lb bag but yields 75% the volume (0.45 / 0.60). That's because the dry-to-wet ratio is essentially the same across bag sizes; the yield difference is just the absolute dry weight.
| Bag size | Yield (ft³ cured) | Bags per ft³ | Bags per yd³ (27 ft³) | Water needed | 2026 typical price |
|---|---|---|---|---|---|
| 40-lb premix | 0.30 ft³ | 3.34 | 90 | ~2 quarts | $5.00–$6.50 |
| 60-lb premix | 0.45 ft³ | 2.23 | 60 | ~3 quarts | $5.50–$7.00 |
| 80-lb premix | 0.60 ft³ | 1.67 | 45 | ~6 pints | $5.75–$7.50 |
| 80-lb high-early strength | 0.60 ft³ | 1.67 | 45 | ~6 pints | $8.50–$11.00 |
| 80-lb fast-setting | 0.60 ft³ | 1.67 | 45 | ~6 pints | $8.00–$10.50 |
| 50-lb post mix (no mixing) | 0.375 ft³ | 2.67 | 72 | Activated in-hole | $5.50–$7.00 |
Bag Count by Project Type (Speed Reference)
Every common DIY concrete project boils down to one of nine project types. Here's the bag count for each at typical dimensions, with the volume calculation shown so you can adjust for your specific size:
| Project | Dimensions | Volume (ft³) | 80-lb bags | 60-lb bags | 2026 cost (80-lb @ $6.50) |
|---|---|---|---|---|---|
| Fence post hole (deep) | 12 in × 36 in deep | 2.4 | 4 | 6 | $26 |
| Mailbox post | 10 in × 24 in deep | 1.1 | 2 | 3 | $13 |
| Deck footing (sonotube) | 10 in × 42 in deep | 1.9 | 4 | 5 | $26 |
| Deck post (4x4 + concrete collar) | 10 in × 36 in | 1.6 | 3 | 4 | $20 |
| Patio pad 8 × 8 × 4 in | 8 ft × 8 ft × 4 in | 21.3 | 36 | 48 | $234 |
| Patio pad 10 × 10 × 4 in | 10 ft × 10 ft × 4 in | 33.3 | 56 | 74 | $364 |
| Patio pad 12 × 12 × 4 in | 12 ft × 12 ft × 4 in | 48.0 | 80 | 107 | $520 |
| Sidewalk section 30 × 4 × 4 in | 30 ft × 4 ft × 4 in | 40.0 | 67 | 89 | $436 |
| Sidewalk section 60 × 4 × 4 in | 60 ft × 4 ft × 4 in | 80.0 | 134 | 178 | $871 |
| Garage floor 20 × 24 × 4 in | 20 ft × 24 ft × 4 in | 160 | 267 | 356 | $1,736 |
| Footing 20 lin ft x 12 × 8 in | 20 ft × 12 in × 8 in | 13.3 | 23 | 30 | $150 |
| Foundation 30 × 30 × 8 in slab | 30 ft × 30 ft × 8 in | 600 | 1,000 | 1,334 | $6,500 |
Fence Posts: The Most-Asked Bag Question
Fence post concrete is the #1 "how many bags" search by volume. The answer depends on three things: post depth (frost line + 6 in below grade, usually 36–42 in in cold-climate US states), hole diameter (3× the post width, typically 10–12 in for a 4x4), and whether you're using regular premix or fast-setting post mix.
| Hole diameter | Hole depth | Hole volume (ft³) | Concrete volume (ft³, post displacement -10%) | 80-lb bags | 60-lb bags |
|---|---|---|---|---|---|
| 8 in | 24 in (warm climate) | 0.70 | 0.63 | 2 | 2 |
| 8 in | 36 in (frost line) | 1.05 | 0.94 | 2 | 3 |
| 10 in | 30 in | 1.36 | 1.23 | 3 | 3 |
| 10 in | 36 in (standard) | 1.64 | 1.47 | 3 | 4 |
| 10 in | 42 in (cold climate) | 1.91 | 1.72 | 3 | 4 |
| 12 in | 36 in | 2.36 | 2.12 | 4 | 5 |
| 12 in | 48 in (heavy gate post) | 3.14 | 2.83 | 5 | 7 |
For 50-lb fast-setting post mix ("just add water to the hole"): 1 bag per 8-in diameter × 30-in deep hole, 2 bags per 10-in diameter × 36-in deep, 3 bags per 12-in diameter. Post mix saves 30–45 minutes per post vs regular premix because no mixing required, but costs 25–40% more per cubic foot of cured concrete. For 4–6 posts: post mix wins on time; for 12+ posts: regular premix + a wheelbarrow saves $40–$70.
60-lb vs 80-lb Bag — Which Saves Money?
Same brand, same store, same shelf: the 80-lb is almost always cheaper per cubic foot of cured concrete. Quikrete 80-lb at $6.50 = $10.83/ft³; Quikrete 60-lb at $5.95 = $13.22/ft³ — the 80-lb is 22% cheaper per finished cubic foot. The 60-lb is cheaper per bag because it weighs less, but you need 33% more of them to fill the same hole.
Pick the 80-lb when: you have a wheelbarrow or mixer, you're pouring more than 4 bags total, you can lift 80 lb (most adults), and the home center carries your preferred brand in 80-lb. Pick the 60-lb when: you're a smaller adult, you're pouring 1–3 bags only, or the project requires carrying bags up stairs / through a tight space. The 40-lb is the right choice only for very small repairs (filling cracks or single post sets) where the 80-lb is overkill.
Reference Tables
| Product | Bag size | Cured yield | PSI | When to use |
|---|---|---|---|---|
| Quikrete Premix Concrete | 80 lb | 0.60 ft³ | 4,000 psi @ 28 days | Default for all general purpose pours |
| Quikrete High Early Strength | 80 lb | 0.60 ft³ | 5,000 psi @ 28 days; 3,000 @ 3 days | Need to load in 3 days; foot traffic in 24 hours |
| Quikrete 5000 (high PSI) | 80 lb | 0.60 ft³ | 5,000 psi @ 28 days | Driveways, garages, heavy-load slabs |
| Quikrete Fast-Setting | 50 lb | 0.375 ft³ | 1,000 psi @ 4 hr; 4,000 @ 28 days | Posts in-hole; no mixing needed |
| Sakrete Maximizer | 80 lb | 0.85 ft³ | 4,000 psi | Same hole, 30% more yield (synthetic aggregate) |
| Sakrete Mix N' Set | 60 lb | 0.45 ft³ | 3,000 psi @ 28 days | General DIY; lighter alternative to 80-lb |
| Sakrete Crack Resistant | 80 lb | 0.60 ft³ | 4,000 psi + fiber | Slabs / patios in freeze-thaw climates |
Pricing varies $5.00–$11.00/bag in 2026 depending on product, region, and home center. Sakrete Maximizer (synthetic aggregate) yields 40% more cured volume per bag than standard 80-lb premix — effectively cheaper per cubic foot despite higher bag price; useful for fence posts and small repairs. Avoid it for slabs because the synthetic aggregate finishes rougher than natural stone.
| Bag size | Water needed | Water:cement ratio (approx) | Slump (target) |
|---|---|---|---|
| 40-lb premix | ~2 quarts (1.9 L) | 0.50 | 4–6 in |
| 60-lb premix | ~3 quarts (2.8 L) | 0.50 | 4–6 in |
| 80-lb premix | ~6 pints (2.8 L) | 0.50 | 4–6 in |
| 80-lb HES / 5000 | ~5.5 pints (2.6 L) | 0.48 | 3–5 in |
Adding too much water (above 0.50 water:cement ratio) drops 28-day strength 25–40% — the single most common DIY concrete mistake. The mix should look like wet sand, not soup. ACI 308R: water mix should hold a 4–6 in slump on a standard cone test.
Bagged vs Ready-Mix Break-Even (1.5 yd³ Cutoff)
The conventional answer ("order ready-mix at 2 yd³") is wrong. The actual break-even is 1.0 to 1.5 cubic yards depending on your local short-load surcharge and labor cost. Here's the math.
| Total volume | 80-lb bags needed | Bagged cost | Ready-mix cost (incl short-load) | Verdict |
|---|---|---|---|---|
| 0.5 yd³ (13.5 ft³) | 23 | $150 | $280+ (1 yd min + $130 short-load) | Bagged wins clearly |
| 1.0 yd³ (27 ft³) | 45 | $293 | $310 (1 yd + $130 short-load = $310) | Toss-up; bagged wins on small budget |
| 1.5 yd³ (40.5 ft³) | 68 | $442 | $385 (1.5 yd + $105 short-load) | Ready-mix wins |
| 2.0 yd³ (54 ft³) | 90 | $585 | $430 (2 yd + $80 short-load) | Ready-mix wins by $155 |
| 3.0 yd³ (81 ft³) | 135 | $878 | $555 (3 yd, no short-load surcharge) | Ready-mix wins by $323 |
| 5.0 yd³ (135 ft³) | 225 | $1,463 | $925 (5 yd full truck) | Ready-mix wins by $538 |
The labor side is invisible in bag-price comparisons but real: mixing 45 bags takes 3–4 hours of physical work with a wheelbarrow or mixer, with cold-joint risk between batches. Ready-mix pours continuous in 30–45 minutes with one tradesman directing the chute. For any pour over ~1 cubic yard, the ready-mix is also better quality concrete (continuous monolithic pour vs batched cold joints) regardless of cost.
The Full Shopping List by Project Size
Beyond the bag count itself, here are the four additional supplies you'll forget at the home center if you don't write them down:
- Wheelbarrow or mixer — rent a 1/2-cf electric mixer ($45/day) for 8+ bags; a wheelbarrow + hoe works for under 8 bags but is back-breaking
- Edge tool / float / trowel — for any flat work. Plan $30–$60 in tool purchases or $20 for a half-day rental kit
- Plastic sheeting (4-mil) — 50-ft roll for $20, used to cure the slab for 7–14 days under shade. Skipping the cure costs you 25–40% of design strength permanently per ACI 308R
- Re-bar or wire mesh — #3 bar at 18 in OC for footings; 6×6 W1.4 wire mesh for any slab over 100 ft². About $0.25–$0.50/ft² in materials
For project-specific calculators that auto-compute bag count alongside cubic yards and rebar: try our concrete calculator (general slab / pour math), the concrete slab calculator (slabs with rebar / mesh), the sonotube calculator (deck footings, fence posts in tubes), the concrete stairs calculator (with IRC R311 riser-tread compliance), or the new concrete sidewalk calculator (with ACI 332 joint-spacing + ADA cross-slope).
Real-World Example Calculations
Worked Example: 6-Post Pergola (24 ft × 14 ft)
Homeowner installing 6 deck footings for a pergola in Wilmington DE. 10-in diameter Sonotube forms, 36-in deep (frost line + 6 in). Regular 80-lb Quikrete.
- Footings
- 6
- Tube diameter
- 10 in
- Depth
- 36 in
- Post in hole?
- Yes, 4x4 (-10% displacement)
Takeaway: For 6 footings, 80-lb wins on cost and labor (16 bags vs 21 bags of 60-lb). At 16 bags total, you're still in bagged-wins territory (below 1 yd³ of concrete); ready-mix doesn't make sense for this scope due to the short-load surcharge. Mix all 16 in 2 batches with a rental mixer (2 hours total + 6 footings to set). Wrap each footing with plastic sheeting for 7-day cure.
Worked Example: 12 × 16 ft Patio Slab (192 ft² × 4 in)
Backyard patio replacement in Newark DE. 12 ft × 16 ft × 4 in thick. 4,000 psi target.
- Length
- 12 ft
- Width
- 16 ft
- Thickness
- 4 in
- Volume
- 12 × 16 × 0.33 = 64 ft³ = 2.37 yd³
Takeaway: At 2.37 yd³ ready-mix wins by $202 on cost AND saves 4+ hours of mixing labor. The 107-bag bagged approach would require 30+ batch cycles in a wheelbarrow or 12+ batch cycles in a rental mixer, with potential cold-joint issues between batches. Call a ready-mix supplier 2 weeks before pour day to schedule a 2.5-yd³ short-load truck.
Next Steps and Related Calculators
When Bag Count Goes Wrong: The Three Mistakes
Three recurring mistakes I see homeowners make on bag estimates — each costs $50–$300 and a wasted Saturday morning:
- Buying 60-lb when 80-lb is right. Default to 80-lb unless you have a specific physical-limit reason. The 60-lb costs 22% more per cubic foot of finished concrete; on a 50-bag project that's $80–$110 wasted.
- Forgetting the displacement adjustment on post holes. When you set a 4x4 wood post in a 10-in diameter hole, the post itself displaces ~10% of the hole volume. Calculate the hole volume, subtract 10%, then run the bag math. Most online calculators give you bag count for the hole, not the actual concrete volume around the post.
- Crossing the ready-mix break-even and not noticing. At 1.5 yd³ you've already crossed into ready-mix-wins territory but the home center will happily sell you 70 bags of 80-lb instead. For any project over 1 cubic yard, call a ready-mix supplier before buying bags; they'll quote in 5 minutes and often beat the bagged total by $100–$300.
This guide pairs well with the concrete mix ratio guide for the PSI selection that determines which premix product to buy, and the concrete curing time chart for the wet-cure window after the bags are mixed and placed. Cross-check against the concrete calculator to see bag count alongside cubic yards and ready-mix cost in one output.
Sources & Standards
These references are used for terminology, safety boundaries, and engineering assumptions. Local code, supplier specifications, and licensed design documents still control your project.
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ASTM C387-23: Standard Specification for Packaged, Dry, Combined Materials for Mortar and Concrete
ASTM International
Referenced for the cured yield specification (0.60 ft³ per 80-lb, 0.45 per 60-lb, 0.30 per 40-lb) for standard packaged concrete premix products.
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Quikrete Concrete Mix #1101 Product Data Sheet (2025 Edition)
Quikrete Companies
Referenced for the bag-specific water requirement (6 pints per 80-lb bag), cured yield, and 28-day PSI rating used in the yield tables and water-ratio reference.
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Sakrete Mix N' Set Product Data Sheet
Sakrete (Oldcastle APG)
Referenced for the Sakrete bag yields and product specifications used in the premium-product comparison table.
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PCA EB001: Design and Control of Concrete Mixtures (16th Edition)
Portland Cement Association
Referenced for the 0.50 water-to-cement ratio target and the relationship between water content and 28-day strength used in the mistakes section.
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ACI 308R-16: Guide to External Curing of Concrete
American Concrete Institute
Referenced for the 7–14 day wet cure requirement after pouring bagged concrete (used in the Shopping List + Worked Examples).
Frequently Asked Questions
How many 80-lb bags of concrete are in a cubic yard?
45 bags of 80-lb premix concrete yield 1 cubic yard of cured concrete (27 ft³ / 0.60 ft³ per 80-lb bag = 45). At $6.50 per bag, that's $292.50 per cubic yard before tax — about $100 more than ready-mix delivered, but ready-mix has minimum order requirements (typically 1–3 yd³) plus a short-load surcharge if you're below the minimum. The break-even between bagged and ready-mix sits at 1.0–1.5 yd³.
How many 60-lb bags of concrete are in a cubic yard?
60 bags of 60-lb premix concrete yield 1 cubic yard of cured concrete (27 ft³ / 0.45 ft³ per 60-lb bag = 60). At $5.95 per bag, that's $357 per cubic yard — 22% more than the equivalent 80-lb bag count, which is why 80-lb is almost always the better buy when both sizes are available. The 60-lb only makes sense if you physically can't lift the 80-lb (smaller adult), if you need very small partial bags (rare), or if it's the only size your home center stocks.
How many bags of concrete for a fence post?
For the standard residential 4x4 wood fence post in a 10-in diameter × 36-in deep hole: 3 bags of 80-lb (or 4 bags of 60-lb) per post. The hole volume is 1.64 ft³; subtract 10% for post displacement = 1.47 ft³ of concrete needed = 2.5 bags rounded up to 3. For gate posts and chain-link tension posts (12-in diameter): 4 bags 80-lb per post. For warm-climate shallow posts (24-in deep): 2 bags 80-lb. Use the calculator above for non-standard geometry, or our sonotube calculator for tube-formed footings.
How much does an 80-lb bag of concrete cost in 2026?
2026 US average: $5.75 to $7.50 per 80-lb bag for standard premix concrete at home centers (Home Depot, Lowe's, Menards). Specialty products run higher: Quikrete 5000 (5,000 psi) $7.00–$8.50; high-early-strength (3-day load capacity) $8.50–$11.00; fast-setting post mix (50-lb) $5.50–$7.00. Buying by the pallet (42 bags) drops the per-bag price 10–15% at most home centers. For 100+ bag orders, call your local concrete supplier directly — they sell pallets at 25–35% below home-center retail.
How long does a bag of concrete last unopened?
Unopened bags of dry premix concrete have a shelf life of 9–12 months when stored above ground in a dry location (Quikrete and Sakrete spec). Bags exposed to humidity (basement, garage floor, outdoor pile) absorb moisture and start hydrating internally; you'll see hard lumps form. Lumps under thumb pressure = still usable; lumps that don't crumble = discard. Once you open a bag, expect 1–4 weeks of usable life depending on humidity. Cold and dry storage extends both; humid summer storage cuts both in half.
Can I mix concrete bags by hand?
Yes, for under 4 bags total. The standard method: dump the bag(s) into a wheelbarrow, form a crater in the middle, pour the water into the crater, fold the dry mix in from the edges with a hoe or shovel. For 4–8 bags, rent a 1/2 cubic foot electric mixer ($40–$50 / day) — saves your back and produces more consistent concrete. For 8+ bags, the mixer is mandatory. The hand-mixing physical demand is real: 4 bags = ~2 hours of upper-body work and is not for the elderly or anyone with shoulder / back issues.
What's the difference between 40, 60 and 80 lb bags?
Only the dry weight (and yield). All three bag sizes contain the same dry-mix product ("premix" = sand + gravel + cement at fixed ratio); the difference is the weight of each bag and therefore the cured volume each produces. 80-lb yields 0.60 ft³, 60-lb yields 0.45 ft³, 40-lb yields 0.30 ft³. The 80-lb is cheapest per cubic foot of cured concrete in 2026 pricing — default to it unless you have a specific reason to choose smaller. The 40-lb makes sense only for very small repairs (1-bag jobs) where the 60-lb is overkill.
How do I know if I need a ready-mix truck instead of bags?
Quick rule: over 1.5 cubic yards of concrete (about 68 bags of 80-lb), call a ready-mix supplier. The math: at 1.5 yd³, bagged costs $442 vs ready-mix $385 including short-load surcharge — ready-mix wins by $57 on materials, plus saves 4+ hours of mixing labor, plus produces continuous-monolithic concrete vs batched cold joints. The break-even can shift earlier (down to 1.0 yd³) in regions with low short-load surcharges, or later (up to 2.0 yd³) in remote areas with high delivery freight. When in doubt, get a ready-mix quote — the call is free and takes 5 minutes.