How the number is worked out
cubic feet = length (ft) × width (ft) × thickness (in) ÷ 12
cubic yards = cubic feet ÷ 27
bags = cubic feet ÷ bag yield, rounded up
Thickness is the one people get wrong: it is entered in inches, so it has to be divided by 12 before it is multiplied with feet. A cubic yard is 3 ft × 3 ft × 3 ft, which is where the 27 comes from.
Bag yields we use
| Bag | Yield per bag | Bags per cubic yard |
|---|---|---|
| QUIKRETE Concrete Mix 40 lb | 0.3 ft³ | 90 |
| QUIKRETE Concrete Mix 50 lb | 0.375 ft³ | 72 |
| QUIKRETE Concrete Mix 60 lb | 0.45 ft³ | 60 |
| QUIKRETE Concrete Mix 80 lb | 0.6 ft³ | 45 |
| QUIKRETE Concrete Mix 90 lb | 0.675 ft³ | 40 |
| QUIKRETE 5000 50 lb | 0.375 ft³ | 72 |
| QUIKRETE 5000 60 lb | 0.45 ft³ | 60 |
| QUIKRETE 5000 80 lb | 0.6 ft³ | 45 |
| QUIKRETE Fast-Setting 50 lb | 0.375 ft³ | 72 |
| QUIKRETE Fast-Setting 60 lb | 0.45 ft³ | 60 |
| Sakrete 5000 Plus 50 lb | 0.38 ft³ | 72 |
| Sakrete 5000 Plus 60 lb | 0.47 ft³ | 58 |
| Sakrete 5000 Plus 80 lb | 0.6 ft³ | 45 |
| Sakrete Fast Setting 50 lb | 0.38 ft³ | 72 |
The yields come from five maker data sheets: QUIKRETE Concrete Mix, QUIKRETE 5000, QUIKRETE Fast-Setting, Sakrete 5000 Plus and Sakrete Fast Setting. Each row links to its sheet, listed with the date we checked it in the sources box below. The table is ours, not a copy of any maker's chart, and the “Bags per cubic yard” column is our own arithmetic: 27 divided by the yield, rounded up. The same bag weight does not always mean the same yield: a 60 lb bag of Sakrete 5000 Plus is listed at 0.47 ft³, a 60 lb bag of QUIKRETE Concrete Mix at 0.45 ft³. If your product isn't listed, read the yield on your own bag before you trust any count, including ours.
How much a cubic yard covers
One cubic yard is 27 ft³, or 27 × 12 = 324 square feet one inch deep. Divide by the thickness in inches:
| Thickness | Area one yd³ covers |
|---|---|
| 4 in | 81 ft² |
| 5 in | 64.8 ft² |
| 6 in | 54 ft² |
These rows are arithmetic for three thicknesses people type in, not a recommendation. How thick your slab has to be is a question for your plans or your local building department.
Worked examples
A 10 ft × 12 ft patio poured 4 in thick:
- 10 × 12 × 4 ÷ 12 = 40 ft³
- 40 ÷ 27 = 1.48 yd³
- 80 lb QUIKRETE Concrete Mix: 40 ÷ 0.60 = 66.7 → 67 bags
- 60 lb QUIKRETE Concrete Mix: 40 ÷ 0.45 = 88.9 → 89 bags
- 60 lb Sakrete 5000 Plus: 40 ÷ 0.47 = 85.1 → 86 bags
That is before any extra for spillage or a subgrade that dips in places. The calculator leaves the extra at 0% on purpose: how much you need depends on how level your base is and how tight your forms are, and we would rather you choose it than hide an assumption inside the answer.
A 10 ft × 10 ft slab, 4 in thick:
- 10 × 10 × 4 ÷ 12 = 33.33 ft³ = 1.23 yd³
- 80 lb QUIKRETE Concrete Mix: 33.33 ÷ 0.60 = 55.6 → 56 bags
- 60 lb QUIKRETE Concrete Mix: 33.33 ÷ 0.45 = 74.1 → 75 bags
- With 10% extra: 33.33 × 1.1 = 36.67 ft³; 36.67 ÷ 0.60 = 61.1 → 62 bags of 80 lb
The 10% follows Sakrete, which suggests adding 10% to estimates as a safety margin (Sakrete calculators). QUIKRETE says its yields are approximate and leave nothing for waste or an uneven base (QUIKRETE calculator), and doesn't give a percentage. Type 10 into the extra box to get the same 62.
Adding your own prices
The two price boxes in the calculator start empty and stay out of the way until you fill one in. Enter what your store charges for the bag you picked and you get bags × that price. Enter what a ready-mix plant quotes per cubic yard and you get cubic yards × that price. Both use the amounts shown above them, including any extra you entered. The ready-mix line is worked out from the unrounded volume, so it can differ by a few cents from the rounded cubic yards shown × your price.
We don't fill in a price for you. Prices change from store to store and week to week, and we have no published figure we could cite. What you type stays on this page: it isn't saved or sent anywhere, and it is gone when you reload.
Questions people ask
How many bags of concrete are in a yard?
It depends on the bag's yield, not just its weight: 27 ÷ yield, rounded up. For QUIKRETE Concrete Mix that is 27 ÷ 0.60 = 45 bags of 80 lb, or 27 ÷ 0.45 = 60 bags of 60 lb. Every bag we list is in the yield table.
How many square feet does a yard of concrete cover?
81 ft² at 4 in, 64.8 ft² at 5 in and 54 ft² at 6 in: 324 ÷ thickness in inches.
How many bags do I need for a 10×10 slab?
At 4 in thick, 33.33 ft³: 56 bags of 80 lb or 75 bags of 60 lb QUIKRETE Concrete Mix with no extra, or 62 bags of 80 lb with 10% extra.
What this calculator is not for
It gives volume, not a design. It does not tell you how thick a slab must be for a driveway or a structure, what reinforcement to use, or what your local code requires. Irregular or sloped slabs need to be split into rectangles and added up, and a thickened edge needs its own line as a footing.
Sources
- QUIKRETE, QUIKRETE® Concrete Mix (No. 1101) — Product Data Sheet. Checked 2026-09-24.
- QUIKRETE, QUIKRETE® 5000 High Early Strength Concrete Mix (No. 1007) — Product Data Sheet. Checked 2026-09-24.
- QUIKRETE, QUIKRETE® Fast-Setting Concrete Mix (No. 1004) — Product Data Sheet (revised November 2025). Checked 2026-09-24.
- Sakrete, Sakrete 5000 Plus High Early Strength Concrete Mix — Technical Data Sheet. Checked 2026-09-24.
- Sakrete, Sakrete Fast Setting Concrete Mix — Technical Data Sheet. Checked 2026-09-24.
- QUIKRETE, QUIKRETE® Quantity Calculator. Checked 2026-09-24.
- Sakrete, Sakrete Calculators. Checked 2026-09-24.
- NIST, NIST Handbook 44 (2026), Appendix C — General Tables of Units of Measurement. Checked 2026-09-24.
“1 728 cubic inches (in3) = 1 cubic foot (ft3) 27 cubic feet = 1 cubic yard (yd3)”