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Yields vary slightly by brand — check the bag.
Allow 5–10%, or 15% for holes bored in sand.
Enter your local store price for a cost estimate.
This concrete bag calculator tells you how many bags of concrete you need for a slab, post hole, footing or any known volume — for 40, 50, 60 and 80 lb bags, plus 20, 25 and 40 kg sizes. It also gives you pallets, mixing water and total cost.
The short answer
One 80 lb bag of concrete yields 0.60 cubic feet, so a cubic yard takes 27 ÷ 0.60 = 45 bags. A 60 lb bag yields 0.45 ft³, so a yard takes 60 bags. A 40 lb bag yields 0.30 ft³ — that’s 90 bags per yard.
To find your own number: work out the volume in cubic feet, then divide by the bag yield. A 10 × 10 ft slab at 4 inches is 33.3 ft³, which is 56 × 80 lb bags before waste.
On this page
How to use this concrete bag calculator
Pick what you’re pouring, enter two or three measurements, and the calculator returns your bag count along with volume, pallets, mixing water and cost. Four modes cover almost every job people buy bagged concrete for:
- Slab — shed floors, garage pads, walkways, patios, equipment pads
- Post holes — fence posts, deck footings, mailbox posts, sign posts
- Footing — strip footings and trenches, measured as a total run
- Known volume — you already have the cubic yards, feet or metres and just want the bag count
Bag size, waste allowance and your local price per bag sit behind Advanced options. The result panel also lists the bag count for every size at once, so you can see straight away whether 60 lb or 80 lb bags work out cheaper at your store.
Working in metric? Switch the toggle in the calculator header to m / mm and the inputs change to metres and millimetres, with 20, 25 and 40 kg bags available in the bag size list.
How many bags of concrete per cubic yard?
This is the number most people are actually looking for. A cubic yard is 27 cubic feet, so the bag count is simply 27 divided by whatever that bag yields.
| Bag size | Yield | Bags per yd³ | Bags per ft³ | Typical use |
|---|---|---|---|---|
| 80 lb | 0.60 ft³ | 45 | 1.7 | Slabs, footings, larger pours |
| 60 lb | 0.45 ft³ | 60 | 2.3 | General purpose, easier to lift |
| 50 lb | 0.375 ft³ | 72 | 2.7 | Fast-setting mixes, repairs |
| 40 lb | 0.30 ft³ | 90 | 3.3 | Post holes, small patches |
Yields are consistent across the major manufacturers because they are calculated from the same mix density, but they can vary by a few percent between products — fast-setting and high-strength formulas in particular. Check the yield printed on the bag and adjust the calculator if yours differs.
The formula behind the calculator
Two steps: find the volume, then divide by the bag yield. The only thing that trips people up is that slab dimensions are in feet while thickness is in inches — divide the inches by 12 before you multiply, or your answer comes out twelve times too big.
Volume (ft³) = Length (ft) × Width (ft) × (Thickness in ÷ 12)
Bags = Volume ÷ Bag yield, rounded up
4 in = 0.333 ft · 5 in = 0.417 ft · 6 in = 0.5 ft
Worked example — 10 × 10 ft slab at 4 inches
At 1.36 cubic yards this is right on the edge of where ready-mix becomes cheaper — see the section below.
Bags of concrete by slab size
Quick reference at 4 inches thick, including a 10% waste allowance. Run your own numbers through the concrete bag calculator above for anything not listed.
| Slab size | Volume | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 4 × 4 ft | 5.9 ft³ | 10 | 14 | 20 |
| 6 × 6 ft | 13.2 ft³ | 23 | 30 | 44 |
| 8 × 8 ft | 23.5 ft³ | 40 | 53 | 79 |
| 10 × 10 ft | 36.7 ft³ | 62 | 82 | 123 |
| 10 × 12 ft | 44.0 ft³ | 74 | 98 | 147 |
| 12 × 12 ft | 52.8 ft³ | 88 | 118 | 176 |
| 12 × 20 ft (1-car drive) | 88.0 ft³ | 147 | 196 | 294 |
| 20 × 20 ft (2-car garage) | 146.7 ft³ | 245 | 326 | 489 |
Notice how fast this gets unreasonable. A two-car garage pad at 245 bags is over five pallets and several tons to move by hand — that job belongs to a ready-mix truck.
How many bags of concrete per post hole?
Post holes are the single most common reason people buy bagged concrete, and the numbers are small enough that bags always make sense. Volume is the circle formula: π × radius² × depth.
| Hole size | Volume | 80 lb bags | 60 lb bags | 50 lb bags |
|---|---|---|---|---|
| 8 in ⌀ × 24 in deep | 0.70 ft³ | 1.2 | 1.6 | 1.9 |
| 10 in ⌀ × 24 in deep | 1.09 ft³ | 1.8 | 2.4 | 2.9 |
| 12 in ⌀ × 24 in deep | 1.57 ft³ | 2.6 | 3.5 | 4.2 |
| 12 in ⌀ × 36 in deep | 2.36 ft³ | 3.9 | 5.2 | 6.3 |
| 12 in ⌀ × 48 in deep | 3.14 ft³ | 5.2 | 7.0 | 8.4 |
Two practical notes. Subtract the post itself if it’s a solid 4 × 4 or 6 × 6 in a tight hole — a 4 × 4 in a 12 inch hole displaces roughly 8% of the volume. And if you’re boring in sand, add 15% rather than 10%, because the sides belly out below grade where you can’t see it.
Hole depth isn’t a preference. Footings for anything structural must extend below the local frost line, which ranges from zero in the southern US to 48 inches or more across the northern states and Canada. Your building department publishes the figure for your area, and it changes your bag count significantly — a 12 inch hole at 48 inches deep needs twice the concrete of the same hole at 24 inches.
Metric bag sizes
Outside the US, bagged concrete comes in 20, 25 and 40 kg sizes and volume is quoted in cubic metres. Switch the calculator to metric and these become available.
| Bag size | Yield | Bags per m³ | Common in |
|---|---|---|---|
| 20 kg | 0.009–0.010 m³ | 100–116 | Australia, New Zealand, UK |
| 25 kg | 0.0125 m³ | 80 | UK, Ireland, Europe |
| 40 kg | 0.020 m³ | 50 | Trade supply, Europe |
Metric yields vary more between brands than US ones do — the 20 kg range spans 0.009 to 0.010 m³, which is a 16% swing in bag count across a cubic metre. Always check the figure printed on the bag before ordering a pallet.
Bags of concrete are not bags of cement
Concrete mix already contains cement, sand and aggregate. You add water and you’re done — that’s what this calculator counts.
Portland cement is one ingredient of three. A standard 1:2:3 mix needs roughly 6 bags of 94 lb cement per cubic yard, plus about 1,500 lb of sand and 1,700 lb of gravel. If a source tells you a cubic yard takes 5 or 6 bags, they mean cement — not concrete mix.
Mixing from raw ingredients is cheaper per yard than bagged concrete mix, but only worth the trouble above roughly half a cubic yard, where you have a mixer and somewhere to store loose aggregate. Below that, the convenience of premixed bags wins easily.
When bags stop making sense
Under 0.5 yd³
Bags win
About 23 × 80 lb bags or fewer. Ready-mix suppliers charge a short-load fee of $150–$300 that erases any per-yard saving.
0.5 – 1 yd³
Call around
23–45 bags is a serious day of mixing. Trailer-mix rental or a short-load delivery is often cheaper once you value your own time.
Over 1 yd³
Order ready-mix
Bagged concrete runs roughly three times the price per yard, and hand-mixing that much means your first batch sets before your last is placed.
There’s a quality argument as well as a cost one. Every bag you mix is its own small batch, and consistency between batches depends entirely on measuring water the same way every time. Ready-mix arrives as one homogeneous load, which is why anything structural above about a yard is better delivered.
How much water does each bag need?
Roughly 3 quarts per 80 lb bag, 2.25 quarts per 60 lb bag and 1.5 quarts per 40 lb bag — but treat these as starting points, not targets. The calculator totals it so you know whether you need a hose or a bucket will do.
Water beyond what the mix needs doesn’t just make it easier to work — it permanently reduces compressive strength and increases shrinkage cracking. Add water gradually and stop as soon as the mix holds its shape when you cut a groove through it with a trowel. If it’s too stiff to place, use a plasticizer, not more water.
Pallets, weight and getting it home
Bagged concrete is heavy, and this catches people out at the store more often than the bag count does.
| Bag size | Bags per pallet | Pallet weight | Yield per pallet |
|---|---|---|---|
| 80 lb | 42 | 3,360 lb | 25.2 ft³ (0.93 yd³) |
| 60 lb | 56 | 3,360 lb | 25.2 ft³ (0.93 yd³) |
| 50 lb | 64 | 3,200 lb | 24.0 ft³ (0.89 yd³) |
| 40 lb | 80 | 3,200 lb | 24.0 ft³ (0.89 yd³) |
A full pallet is over 3,000 lb — more than the payload of most half-ton pickups. If you need a pallet or more, arrange store delivery. And note that a pallet of any size yields under one cubic yard, which is a useful gut check: if your project needs more than one pallet, it probably needs a truck.
Mistakes this calculator prevents
- Forgetting to convert inches to feet. Multiplying feet by inches gives an answer twelve times too large.
- Using diameter instead of radius on post holes — that’s four times too much concrete.
- Confusing cement bags with concrete mix bags. Completely different products and quantities.
- Buying no extra. Bags are cheap; a second trip to the store mid-pour is not.
- Ignoring frost depth and sizing holes too shallow for the local code.
- Underestimating weight. Half a yard of concrete mix is around 2,000 lb of bags to lift twice.
- Rounding down. Always round bag counts up — you cannot buy 0.4 of a bag.
Frequently asked questions
How many 80 lb bags of concrete make a yard?
45 bags. An 80 lb bag yields 0.60 cubic feet and a cubic yard is 27 cubic feet, so 27 ÷ 0.60 = 45. Add a waste allowance and most people buy 48–50 for a full yard.
How many 60 lb bags of concrete are in a yard?
60 bags. A 60 lb bag yields 0.45 cubic feet, and 27 ÷ 0.45 = 60. That’s 1.07 pallets, so a full yard in 60 lb bags means buying more than one pallet.
How many bags of concrete do I need for a 10 × 10 slab?
At 4 inches thick, a 10 × 10 ft slab is 33.3 cubic feet, or 36.7 with 10% waste. That’s 62 × 80 lb bags, 82 × 60 lb bags, or 123 × 40 lb bags. At 1.36 cubic yards, this is around the point where ready-mix becomes cheaper.
How many bags of concrete per fence post?
A 12 inch diameter hole at 24 inches deep takes about 1.57 cubic feet, which is roughly 2.6 × 80 lb bags or 3.5 × 60 lb bags. Most people budget 2–3 bags per post. Deeper holes in cold-climate frost zones need considerably more.
How much does a bag of concrete cover?
An 80 lb bag yields 0.60 cubic feet, which covers about 1.8 square feet at 4 inches thick, or 3.6 square feet at 2 inches. A 60 lb bag covers roughly 1.35 square feet at 4 inches. Coverage always depends on thickness, so convert to volume rather than working in area.
Is it cheaper to buy bags of concrete or ready-mix?
Bagged concrete costs roughly three times as much per cubic yard as ready-mix delivered. But below about half a cubic yard, short-load fees make ready-mix the more expensive option overall. The crossover point is usually between 0.5 and 1 cubic yard.
How much water do you add to a bag of concrete?
About 3 quarts for an 80 lb bag, 2.25 quarts for 60 lb and 1.5 quarts for 40 lb. Add it gradually — extra water permanently reduces strength and increases cracking. Stop when the mix holds a groove cut with a trowel.
How many bags of concrete are on a pallet?
Typically 42 × 80 lb bags, 56 × 60 lb, 64 × 50 lb or 80 × 40 lb. Every configuration weighs roughly 3,200–3,400 lb and yields just under one cubic yard. That exceeds the payload of most half-ton pickups, so arrange delivery.
How many bags of concrete in a cubic metre?
Between 100 and 116 × 20 kg bags depending on brand, 80 × 25 kg bags, or 50 × 40 kg bags. In US sizes a cubic metre takes about 59 × 80 lb bags. Metric yields vary more between manufacturers, so check the bag.
Can one person mix a lot of bags by hand?
Realistically, one person with a wheelbarrow manages 10–15 bags an hour, and a portable mixer roughly doubles that. Beyond about 30 bags you need a second person, because concrete has to be placed continuously — stopping creates a cold joint that permanently weakens the pour.
Do I need to add waste to my bag count?
Yes — 10% is a sensible default, 15% for holes bored in loose or sandy soil where the sides belly out. Spilled mix, uneven sub-base and slight over-digging all consume more than expected, and running out mid-pour is far more costly than a few spare bags.
Does bagged concrete expire?
It doesn’t have a hard expiry, but cement absorbs moisture from the air and gradually hydrates. Bags stored dry and off the ground are usually fine for six to twelve months. If a bag has hard lumps that don’t break up under hand pressure, it has partially set and will not reach full strength.
Standards and sources
- ASTM C94 — Standard specification for ready-mixed concrete
- ACI 318 — Building code requirements for structural concrete
- ACI 301 — Specifications for structural concrete, including mix water limits
- Published bag yield and pallet quantity data from major concrete mix manufacturers
- Local building department frost depth requirements (vary by jurisdiction)
Related calculators
Concrete Slab CalculatorSlab volume with mesh and edge beams
Post Hole Concrete CalculatorBags per post and depth guidance
Concrete Slab Cost CalculatorCompare bagged against ready-mix
Cubic Yards CalculatorConvert any volume to yd³
Concrete Mix CalculatorCement, sand and gravel ratios
How this concrete bag calculator works out its numbers
Volume is calculated with standard geometric formulas, with every input normalised to feet before multiplication. Bag yields are 0.60 ft³ for 80 lb, 0.45 ft³ for 60 lb, 0.375 ft³ for 50 lb and 0.30 ft³ for 40 lb, matching published manufacturer figures; metric equivalents are 0.010 m³ for 20 kg, 0.0125 m³ for 25 kg and 0.020 m³ for 40 kg. Finished weight assumes 150 lb per cubic foot (about 2,400 kg/m³). Pallet quantities and mixing water volumes follow typical manufacturer specifications and can vary by product line, particularly for fast-setting and high-strength mixes.
Cost estimates use the price per bag you enter, so they reflect your local store rather than a national average.
This calculator produces quantities, not structural design. Slab thickness, footing depth, reinforcement and frost-depth requirements must come from your local building code and, for anything structural, a qualified engineer. Frost depth in particular varies widely by jurisdiction and directly affects how much concrete a footing needs.