★ CONSTRUCTION · CONCRETE · REFERENCE TABLE
62 eighty-pound bags for a 10 x 10 ft slab. That is 33.33 cu ft of concrete, 36.67 cu ft with 10% waste, 4,960 lb in all, at $341.00. Every bag size from 40-lb to 80-lb is in the chart below, with bags per cubic yard — pick a size in the calculator, or price any slab.
Pick a bag size for the yield, or enter the slab and let the calculator count the bags: the volume is the length times the width times the thickness, the waste goes on top, and the bags are the need divided by the yield, rounded up — so the number you get is the number to buy.
Every standard bag size, with its yield in cubic feet and cubic yards and how many bags make a cubic yard. The bigger the bag, the fewer bags you carry: an 80-lb bag yields twice the concrete of a 40-lb bag, so a cubic yard takes 45 eighty-pound bags against 90 forty-pound bags. The yields are the standard bag yields for pre-mixed concrete.
| Bag size | Yield (cu ft) | Yield (cu yd) | Bags per cu yd |
|---|---|---|---|
| 40-lb | 0.30 cu ft | 0.0111 cu yd | 90 |
| 50-lb | 0.375 cu ft | 0.0139 cu yd | 72 |
| 60-lb | 0.45 cu ft | 0.0167 cu yd | 60 |
| 80-lb | 0.60 cu ft | 0.0222 cu yd | 45 |
A bag count is three steps: the volume of the slab, the waste on top of it, and the yield of the bag you buy. The volume is the length times the width times the thickness in inches divided by 12, in cubic feet. Add the waste percent for spillage and uneven ground, then divide by the yield per bag and round up — you cannot buy part of a bag, and running short mid-pour is the expensive mistake.
At the defaults — a 10 x 10 ft slab, 4 in thick, 80-lb bags, 10% waste, $5.50 a bag — the volume is 10 × 10 × 4 ÷ 12 = 33.33 cu ft, the need with waste is 33.33 × 1.10 = 36.67 cu ft, and the bags are 36.67 ÷ 0.60 = 61.11, rounded up to 62 bags. That is 62 × 80 = 4,960 lb in all, at 62 × $5.50 = $341.00.
| Case | Volume (cu ft) | Needed (cu ft) | Bags | Cost |
|---|---|---|---|---|
| Default (10 x 10 ft, 4 in, 80-lb, 10% waste) | 33.33 | 36.67 | 62 | $341.00 |
| 60-lb bags | 33.33 | 36.67 | 82 | $451.00 |
| 50-lb bags | 33.33 | 36.67 | 98 | $539.00 |
| 40-lb bags | 33.33 | 36.67 | 123 | $676.50 |
| 4 x 4 ft patio (4 in) | 5.33 | 5.87 | 10 | $55.00 |
| 20 x 20 ft slab (4 in) | 133.33 | 146.67 | 245 | $1,347.50 |
| 6-in thick 10 x 10 ft | 50.00 | 55.00 | 92 | $506.00 |
| Waste 0% | 33.33 | 33.33 | 56 | $308.00 |
| 12 x 12 ft slab (4 in) | 48.00 | 52.80 | 88 | $484.00 |
Setup: 10 x 10 ft slab, 4 in thick, 80-lb bags, 10% waste, $5.50 a bag.
Line 1 — the volume. 10 × 10 × 4 ÷ 12 = 33.33 cu ft.
Line 2 — the waste. 33.33 × 1.10 = 36.67 cu ft needed.
Line 3 — the bags. 36.67 ÷ 0.60 = 61.11, rounded up to 62 bags.
Line 4 — the weight. 62 × 80 = 4,960 lb in all.
Line 5 — the cost. 62 × $5.50 = $341.00.
Reverse: a $200 budget buys 36 bags, or 21.60 cu ft; a $500 budget buys 90 bags, or 54.00 cu ft. One cubic yard with 10% waste takes 50 eighty-pound bags. The 62 bags cover 37.20 cu ft, which is 111.60 sq ft at 4 in thick.
60-lb bags: the same 36.67 cu ft need is 36.67 ÷ 0.45 = 81.48, rounded up to 82 bags at $451.00. Smaller bags mean more bags and more money at the same price a bag, because each bag holds less concrete.
50-lb bags: 36.67 ÷ 0.375 = 97.78, rounded up to 98 bags at $539.00. The 50-lb bag is easier to lift, but you carry 36 more bags than the 80-lb case.
40-lb bags: 36.67 ÷ 0.30 = 122.22, rounded up to 123 bags at $676.50. The 40-lb bag nearly doubles the bag count and the cost at the same price a bag.
4 x 4 ft patio: the volume is 4 × 4 × 4 ÷ 12 = 5.33 cu ft, the need with waste is 5.87 cu ft, and the bags are 5.87 ÷ 0.60 = 9.78, rounded up to 10 bags at $55.00. A small patio is a ten-bag job.
20 x 20 ft slab: the volume is 20 × 20 × 4 ÷ 12 = 133.33 cu ft, the need with waste is 146.67 cu ft, and the bags are 146.67 ÷ 0.60 = 244.44, rounded up to 245 bags at $1,347.50. Four times the area is four times the bags, and at this size a ready-mix truck is worth pricing.
6-in thick slab: the volume is 10 × 10 × 6 ÷ 12 = 50.00 cu ft, the need with waste is 55.00 cu ft, and the bags are 55.00 ÷ 0.60 = 91.67, rounded up to 92 bags at $506.00. Two more inches of thickness is half as much concrete again.
Waste 0%: with no waste the need is the volume itself, 33.33 cu ft, and the bags are 33.33 ÷ 0.60 = 55.56, rounded up to 56 bags at $308.00. Skipping the waste saves 6 bags, but a short pour costs more than 6 bags.
12 x 12 ft slab: the volume is 12 × 12 × 4 ÷ 12 = 48.00 cu ft, the need with waste is 52.80 cu ft, and the bags are 52.80 ÷ 0.60 = 88, exactly 88 bags at $484.00. No rounding up needed here: the need divides evenly by the yield.
Reverse — the budget and the yard: a $200 budget buys 200 ÷ $5.50 = 36 bags, or 36 × 0.60 = 21.60 cu ft; a $500 budget buys 90 bags, or 54.00 cu ft. One cubic yard is 27 cu ft, and with 10% waste that is 29.70 cu ft, which takes 29.70 ÷ 0.60 = 49.50, rounded up to 50 eighty-pound bags. The 62 bags cover 62 × 0.60 = 37.20 cu ft, which is 37.20 ÷ (4 ÷ 12) = 111.60 sq ft at 4 in thick.
The chart uses the standard bag yields for pre-mixed concrete: 0.30 cu ft for a 40-lb bag, 0.375 for 50-lb, 0.45 for 60-lb, and 0.60 for 80-lb. It assumes a flat slab of even thickness, the same waste percent across the pour, and the same price per bag whatever the size. It leaves out the water, the formwork, the reinforcement, and the labour, and it is explicitly not a structural or mix-design engineering chart: the bag count tells you how much concrete to buy, not how strong the slab will be. Rounding convention: volumes are shown to two decimals, bags are always rounded up to a whole bag, and money is rounded to cents, all computed from unrounded values.
| Output | Formula | What it means |
|---|---|---|
| Slab volume | length × width × thickness ÷ 12 | 33.33 cu ft. |
| Needed with waste | volume × (1 + waste%) | 36.67 cu ft. |
| Yield per bag | table row for the bag size | 0.60 cu ft/bag. |
| Bags | ceil(needed ÷ yield) | 62 bags. |
| Total weight | bags × bag size | 4,960 lb. |
| Cost | bags × price per bag | $341.00. |
| 60-lb bags | same model, 60-lb bags | 82 bags, $451.00 (volume 33.33 cu ft, need 36.67 cu ft). |
| 50-lb bags | same model, 50-lb bags | 98 bags, $539.00 (volume 33.33 cu ft, need 36.67 cu ft). |
| 40-lb bags | same model, 40-lb bags | 123 bags, $676.50 (volume 33.33 cu ft, need 36.67 cu ft). |
| 4 x 4 ft patio | same model, 4 x 4 ft | 10 bags, $55.00 (volume 5.33 cu ft, need 5.87 cu ft). |
| 20 x 20 ft slab | same model, 20 x 20 ft | 245 bags, $1,347.50 (volume 133.33 cu ft, need 146.67 cu ft). |
| 6-in thick slab | same model, 6 in thick | 92 bags, $506.00 (volume 50.00 cu ft, need 55.00 cu ft). |
| Waste 0% | same model, 0% waste | 56 bags, $308.00 (volume 33.33 cu ft, need 33.33 cu ft). |
| 12 x 12 ft slab | same model, 12 x 12 ft | 88 bags, $484.00 (volume 48.00 cu ft, need 52.80 cu ft). |
| Reverse: $200 budget | floor(budget ÷ price) | 36 bags = 21.60 cu ft. |
| Reverse: $500 budget | floor(budget ÷ price) | 90 bags = 54.00 cu ft. |
| Reverse: 1 cu yd + 10% waste | ceil(27 × 1.10 ÷ yield) | 50 bags. |
| Reverse: bags cover | bags × yield; ÷ thickness | 37.20 cu ft = 111.60 sq ft at 4 in. |
The math is exact for the numbers you enter: the volume is the length times the width times the thickness divided by 12, the need is the volume times one plus the waste, and the bags are the need divided by the yield, rounded up to a whole bag. What the chart cannot do is size the slab for the job: check the thickness and the reinforcement on the plans, because a 4-in patio slab and a driveway slab are different jobs. The yields are the standard bag yields for pre-mixed concrete, and the price a bag is the price you enter. This is not a structural or mix-design engineering chart. For the slab volume itself, see concrete slab calculator; for the mix behind the bags, see concrete mix calculator.
Bright Side Kit. "Concrete Bag Chart: Bags Per Slab & Cubic Yard 2026." https://brightoolbox.com/concrete-bag-chart/ Accessed October 25, 2026.62 eighty-pound bags. A 10 x 10 ft slab at 4 in thick is 33.33 cu ft, and with 10% waste you need 36.67 cu ft, which is 62 bags of 80-lb mix at $341.00. With 60-lb bags it is 82 bags, and with 40-lb bags it is 123.
45 bags, before waste. An 80-lb bag yields 0.60 cu ft, and a cubic yard is 27 cu ft, so 27 ÷ 0.60 = 45 bags. With 10% waste a cubic yard takes 50 eighty-pound bags.
It depends on the bag. A 40-lb bag yields 0.30 cu ft, a 50-lb bag 0.375 cu ft, a 60-lb bag 0.45 cu ft, and an 80-lb bag 0.60 cu ft — so one cubic foot takes about 1.67 eighty-pound bags, or 3.33 forty-pound bags.
Volume, waste, then round up. The volume is length × width × thickness ÷ 12 in cubic feet, add the waste percent, then divide by the yield per bag and round up to a whole bag. At the defaults that is 33.33 cu ft, 36.67 cu ft with waste, and 62 eighty-pound bags.
About 80 lb a bag, dry, for an 80-lb bag. The 62 bags in the default slab weigh 4,960 lb dry in all. Water adds weight once mixed, so plan the carrying and the barrow trips on the dry weight plus the water.
80-lb bags for a slab, smaller bags for small jobs. The 80-lb bag is the cheapest per cubic foot and the fewest bags to carry, but each one weighs 80 lb. For a 4 x 4 ft patio, 10 eighty-pound bags do the job at $55.00; for a small repair, 40-lb bags are easier to lift.
36 eighty-pound bags, or 21.60 cu ft. At $5.50 a bag, $200 buys 36 bags. A $500 budget buys 90 bags, or 54.00 cu ft — two cubic yards, before waste.
No. This is a bag-count and volume chart only — it is not a structural or mix-design engineering chart. For footings, foundations and load-bearing work, check the building code and an engineer, not a bag chart.