Concrete Bags from Volume and Bag Yield
Also known as how many bags of concrete · concrete mix bags
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Bagged concrete is bought by yield, not by weight, and the yield is printed on the bag: an 80 lb bag of standard premix makes about 0.60 ft³, a 60 lb bag about 0.45 ft³, a 30 kg Canadian bag about 13.5 L. Work out the volume of the pour, divide by the yield, and round up — a footing that comes up two inches short at the end of the day cannot be fixed with a second batch tomorrow.
The crossover point is worth knowing before you start hauling. One cubic yard is 27 ft³, which is 45 bags of 80 lb premix, over 1.5 tonnes of material and most of a morning in a mixer. Anything past roughly half a yard is usually cheaper and far easier as ready-mix delivered, even after the short-load fee. Bags earn their place on posts, small pads, repairs and anywhere a truck simply cannot reach.
Two things this number does not include: the extra for over-excavated footing bottoms and irregular formwork, which is what the separate waste allowance is for, and the water. Yield figures assume the bag is mixed to the specified water content, not soupy.
- = Bags required
- = Volume of the pour
- = Yield per bag
- Bags required — Studs on a Wall at a Given Spacing, Stair Riser Count from Total Rise
- Volume of the pour — Truck Loads from Bank Volume and Swell, Cone Frustum Volume (Truncated Cone)
- Yield per bag — Truck Loads from Bank Volume and Swell, Fuel Consumption (L/100 km)