How Many Bags of Concrete in a Yard? 40, 50, 60, 80 lb and 25/30 kg
A cubic yard of concrete is 45 bags of 80 lb premix, or 60 bags of 60 lb. Below is the math, a table for every common bag size, and bag counts for typical slabs.
The short answer
A cubic yard is 27 cubic feet. Divide that by what one bag makes once it’s mixed (its yield), and you have the number of bags. QUIKRETE’s Concrete Mix data sheet lists these yields: about 0.30 ft³ for a 40 lb bag, 0.45 ft³ for a 60 lb bag and 0.60 ft³ for an 80 lb bag. Its Fast-Setting mix lists 0.375 ft³ for a 50 lb bag. So:
| Bag size | Yield per bag | Bags per cubic yard | Bags per cubic metre |
|---|---|---|---|
| 40 lb | 0.30 ft³ / 8.5 L | 90 | 118 |
| 50 lb | 0.375 ft³ / 10.6 L | 72 | 95 |
| 60 lb | 0.45 ft³ / 12.7 L | 60 | 79 |
| 80 lb | 0.60 ft³ / 17 L | 45 | 59 |
| 25 kg (Canada) | 11.6 L | 66 | 87 |
| 30 kg (Canada) | 14 L | 55 | 72 |
Why the yield matters more than the weight
It’s tempting to work from weight alone, but the number printed on the bag that matters is the yield. Two bags of the same weight can make slightly different volumes depending on the aggregate in the mix and the water you add. QUIKRETE’s instructions start with about 6 pints (2.8 L) of water per 80 lb bag, with a final water content of roughly 6–9 pints (2.8–4.3 L). That water is part of the volume you end up with. When the bag lists a yield, use it. When it doesn’t, the figures above are a reasonable starting point for standard concrete mix.
Bag counts for common 4 in slabs
Most patios, shed bases and walkways are poured around 4 in thick. Here is what common footprints need before any extra, then with 10% added for an uneven base and spills:
| Slab (4 in thick) | Volume | 80 lb bags | 60 lb bags | 80 lb bags + 10% |
|---|---|---|---|---|
| 8 × 8 ft | 21.3 ft³ (0.79 yd³) | 36 | 48 | 40 |
| 10 × 10 ft | 33.3 ft³ (1.23 yd³) | 56 | 75 | 62 |
| 10 × 12 ft | 40.0 ft³ (1.48 yd³) | 67 | 89 | 74 |
| 12 × 12 ft | 48.0 ft³ (1.78 yd³) | 80 | 107 | 88 |
| 10 × 20 ft | 66.7 ft³ (2.47 yd³) | 112 | 149 | 123 |
For other sizes or thicknesses, the concrete calculator does the same arithmetic for slabs, round columns and steps, in imperial or metric.
The formula, step by step
- Volume in cubic feet = length (ft) × width (ft) × thickness (in) ÷ 12.
- Add extra: multiply by 1.05 for 5% or 1.10 for 10%.
- Bags = volume ÷ yield per bag, rounded up to a whole bag.
QUIKRETE’s own training material walks through the same method with a 10 × 6 ft slab, 4 in thick: 20 ft³, which it rounds to 33 bags of 80 lb. Strictly, 20 ÷ 0.6 = 33.3, so rounding up gives 34. Rounding down by a fraction of a bag rarely matters, but it’s one more reason to add a margin.
In metric: volume (m³) = length (m) × width (m) × thickness (mm) ÷ 1000, then divide the litres by the bag yield in litres. A 3 × 2.5 m base at 100 mm is 0.75 m³ (750 L). That’s 65 bags of 25 kg at 11.6 L each, before any extra.
When to stop counting bags
Bags make sense for small jobs, places a truck can’t reach, and pours you can mix in stages. They get heavy fast, though. A cubic yard in 80 lb bags is 45 × 80 = 3,600 lb (about 1.6 tonnes) to lift, carry, mix and place. For a slab of a couple of yards or more, get a ready-mix quote too. Include any short-load charge, then compare it with the bags plus mixer hire and the labour of mixing everything before it starts to set.
Common mistakes
- Forgetting to divide inches by 12. A 4 in slab is 0.333 ft thick, not 4 ft.
- Using the dry weight as volume. An 80 lb bag doesn’t make anything close to a cubic foot. It makes 0.6 ft³.
- Measuring the plan instead of the dig. Measure the depth inside the forms in several places. If the base dips, the slab gets thicker there and uses more concrete.
- Running out mid-pour. A pour that stops leaves a weak joint. Have a few spare bags; unopened bags can be stored dry for the next job.
Frequently asked questions
How many 80 lb bags of concrete are in a yard?
45. A cubic yard is 27 ft³ and an 80 lb bag yields about 0.60 ft³.
How many 60 lb bags are in a yard?
60, because each 60 lb bag yields about 0.45 ft³.
How many bags of concrete make a cubic metre?
About 59 bags of 80 lb, 79 bags of 60 lb, 87 bags of 25 kg (11.6 L) or 72 bags of 30 kg (14 L), always rounded up.
How many bags do I need for a 10 × 10 slab?
At 4 in thick it is 33.3 ft³, which is 56 bags of 80 lb, or 62 bags with 10% extra.