A standard bag of concrete mix yields 0.30 cubic feet at 40 lb, 0.375 at 50 lb, 0.45 at 60 lb, 0.60 at 80 lb and 0.675 at 90 lb. That puts 45 bags of 80 lb in a cubic yard. Those are published numbers, not estimates — and three common products do not follow them.
Yield by bag size, from the data sheets
Yield is the volume of finished concrete one bag makes once it is mixed. It is printed on every manufacturer's data sheet, and it is the only number worth calculating from. The figures below come straight off those sheets.
| Product | 40 lb | 50 lb | 60 lb | 80 lb | 90 lb |
|---|---|---|---|---|---|
| QUIKRETE Concrete Mix (No. 1101) | 0.30 | 0.375 | 0.45 | 0.60 | 0.675 |
| QUIKRETE 5000 (No. 1007) | — | 0.375 | 0.45 | 0.60 | — |
| QUIKRETE Fast-Setting (No. 1004) | — | 0.375 | 0.45 | — | — |
| Sakrete High-Strength | 0.30 | — | 0.45 | 0.60 | 0.66 |
| Sakrete 5000 Plus | — | 0.38 | 0.47 | 0.60 | — |
| Sakrete Fast Setting | — | 0.38 | — | — | — |
| Sakrete Maximizer (lightweight) | 0.46 | — | — | 0.92 | — |
QUIKRETE also publishes metric-only sizes for the Canadian market: a 25 kg (55 lb) bag of Fast-Setting yields 0.41 cubic feet and a 30 kg (66 lb) bag yields 0.50.
How many bags make a cubic yard
A cubic yard is 27 cubic feet. Divide 27 by the yield and round up, and you have the bag count — along with the pile of dry mix you are about to move by hand.
| Bag | Yield | Bags per yd³ | Dry mix to carry |
|---|---|---|---|
| 40 lb | 0.30 ft³ | 90 | 3,600 lb |
| 50 lb | 0.375 ft³ | 72 | 3,600 lb |
| 60 lb | 0.45 ft³ | 60 | 3,600 lb |
| 80 lb | 0.60 ft³ | 45 | 3,600 lb |
| 90 lb | 0.675 ft³ | 40 | 3,600 lb |
| 80 lb high-yield | 0.92 ft³ | 30 | 2,400 lb |
Notice that the standard mixes all land on the same 3,600 lb. That is not a coincidence: every one of them yields 0.0075 cubic feet per pound of dry mix, so the bag size changes how many trips you make, not how much you carry. The lightweight mix is the exception, and it is the only way to move less material for the same hole.
What one bag covers, by thickness
Coverage is the yield divided by the thickness in feet. A 4 inch slab is a third of a foot, so an 80 lb bag covers 0.60 divided by 0.333, which is 1.8 square feet.
| Bag | 2 in | 3 in | 4 in | 5 in | 6 in |
|---|---|---|---|---|---|
| 40 lb (0.30 ft³) | 1.80 ft² | 1.20 ft² | 0.90 ft² | 0.72 ft² | 0.60 ft² |
| 60 lb (0.45 ft³) | 2.70 ft² | 1.80 ft² | 1.35 ft² | 1.08 ft² | 0.90 ft² |
| 80 lb (0.60 ft³) | 3.60 ft² | 2.40 ft² | 1.80 ft² | 1.44 ft² | 1.20 ft² |
| 80 lb high-yield (0.92 ft³) | 5.52 ft² | 3.68 ft² | 2.76 ft² | 2.21 ft² | 1.84 ft² |
To turn an area into a bag count without doing this by hand, the concrete bag calculator takes the dimensions and the bag size and rounds up after a waste allowance. For a slab or pad, the slab calculator gives you the ready-mix yardage alongside the bag count so you can compare the two.
Where the yields actually differ
Most of the time the brands agree and you can use the standard column. Three cases break that rule, and each of them changes a bag count.
- Sakrete 5000 Plus, 60 lb: 0.47 ft³, not 0.45. Small on one bag, real on a job. Fifty-eight bags make a cubic yard instead of 60, and a bag count worked out at 0.45 will have you buying about 4% more than you need.
- The 90 lb bags disagree. QUIKRETE publishes 0.675 ft³, Sakrete High-Strength 0.66. That is 40 bags per cubic yard against 41.
- High-yield lightweight mixes are a different product. Sakrete Maximizer lists 0.92 ft³ for an 80 lb bag and 0.46 for a 40 lb bag — 53% more volume per pound than a standard mix, because the aggregate is structural lightweight rather than gravel. Its cured density is 105 to 120 lb per cubic foot instead of the usual 140 to 150. Fewer bags and less weight to carry, at a density that a structural drawing may or may not accept.
The rule that follows from all three: look up the bag in your hand. Yield is a property of the product, not of the weight printed on the front.
Why a bag does not make its weight divided by 145
This one trips up people who know their concrete weights. Normalweight concrete runs 140 to 150 lb per cubic foot, per NRMCA CIP 36. So an 80 lb bag ought to make 80 divided by 145, which is 0.55 cubic feet. The data sheet says 0.60. Where does the extra volume come from?
From the water. The same QUIKRETE data sheet calls for about 6 pints of water per 80 lb bag, and 6 pints is three quarters of a gallon, which weighs about 6.3 lb. Now do the arithmetic on the finished concrete instead of the dry mix:
The same check works on a whole cubic yard: 45 bags is 3,600 lb of dry mix plus about 34 gallons of water, roughly 3,880 lb in 27 cubic feet, or 144 lb per cubic foot again. The published yield and the published density agree, as long as you remember that the water is part of the concrete and not something that evaporates out of it.
Water and mixer capacity
Water is a range with a hard ceiling, not a target. QUIKRETE's Table 2 gives both ends for every size.
| Bag | Starting water | Maximum expected |
|---|---|---|
| 40 lb | 3 pt | 4.5 pt |
| 50 lb | 3.5 pt | 5.5 pt |
| 60 lb | 4 pt | 7 pt |
| 80 lb | 6 pt | 9 pt |
| 90 lb | 7 pt | 10 pt |
Mix to a stiff, moldable consistency — the data sheet targets a 2 to 3 inch slump. Water beyond the maximum reduces strength, and it is the single easiest way to ruin a pour that was otherwise going fine.
On mixer size, QUIKRETE asks for at least 1 cubic foot of mixer capacity per 80 lb bag mixed at one time, so a typical 3.5 ft³ portable mixer takes three bags a batch. Fast-setting mix is tighter still — 3/4 of a cubic foot per 50 lb bag — and it gives you 20 to 40 minutes before final set, which is why nobody batches more of it than they can place. For a fence post, the fast-setting product is not mixed at all: the fence post calculator follows the manufacturers' dry method, where the mix goes into the hole and the water goes on top.
Bottom line
- Standard yields: 0.30 / 0.375 / 0.45 / 0.60 / 0.675 ft³ for 40 / 50 / 60 / 80 / 90 lb.
- Bags per cubic yard: 90 / 72 / 60 / 45 / 40 — and 3,600 lb of dry mix either way.
- Three exceptions worth checking: Sakrete 5000 Plus at 60 lb (0.47), the 90 lb bags (0.66 against 0.675), and high-yield lightweight mixes (0.92 at 80 lb).
- Yield already counts the mixing water. That is why 80 lb makes 0.60 ft³ and not 0.55.
- Bagged mix is for 2 inches and thicker, and past a cubic yard the truck usually wins.