Work out how many Quikrete bags a slab, post hole or column needs, using yields from the published data sheets. See water, weight and the same job in Australian 20 kg bags. This is an independent tool from ConcreteCreek.
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| Bag | Bags | Total Weight |
|---|
Quikrete sizes for the chosen product, plus an Australian 20 kg bag at 0.0093 m³.
Bags Needed
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This Quikrete concrete calculator counts bags from published yields, then shows the same job in Australian units.
For post holes, pick Fast-Setting if you want the mix sold for setting posts. For a broader Australian count, the concrete bag calculator covers local brands.
Independent tool. ConcreteCreek is not affiliated with, sponsored by or endorsed by the maker of QUIKRETE products. QUIKRETE is a trademark of its owner, and we use the name only to say which product data this page is based on. For official information, see the maker's own Quikrete calculator and data sheets.
Quikrete is an American brand of bagged concrete. People in Australia meet the name in American videos and how-to guides, then want to know what those bag counts mean here. That is the gap this page fills.
The figures come from the published data sheets for each mix. Always follow the label on the bag in your hand, since products and yields can change. This page doesn't choose thickness, strength or reinforcement for your job.
Yield is how much mixed concrete one bag makes. The Concrete Mix data sheet lists these yields. Fast-Setting, 5000 and Crack-Resistant mixes list the same yields at the sizes they share.
| Bag | Weight | Yield | Litres |
|---|---|---|---|
| 40 lb | 18.1 kg | 0.3 ft³ | 8.5 L |
| 50 lb | 22.7 kg | 0.375 ft³ | 10.6 L |
| 60 lb | 27.2 kg | 0.45 ft³ | 12.7 L |
| 80 lb | 36.3 kg | 0.6 ft³ | 17 L |
| 90 lb | 40.8 kg | 0.675 ft³ | 19.1 L |
Notice the pattern. Each pound of bag makes 0.0075 cubic feet of concrete, so a bigger bag simply scales up. The 90 lb bag has regional availability, according to the sheet.
| Bag | Per Cubic Foot | Per Cubic Yard | Per Cubic Metre |
|---|---|---|---|
| 40 lb | 3.3 | 90 | 118 |
| 50 lb | 2.7 | 72 | 95 |
| 60 lb | 2.2 | 60 | 79 |
| 80 lb | 1.7 | 45 | 59 |
| 90 lb | 1.5 | 40 | 53 |
| 20 kg (Australia) | 3.0 | 83 | 108 |
Counts are rounded up and have no extra allowance. A yard of concrete takes 45 of the 80 lb bags, which is 3,600 lb, or about 1.6 tonnes, to lift. For yard conversions, see the concrete cubic yard calculator and the cubic yards to cubic feet concrete calculator.
Slab volume (ft³) = length (ft) × width (ft) × depth (in) ÷ 12
Bags = volume (ft³) × (1 + extra %) ÷ yield per bag, rounded up
Post hole (ft³) = (3.1416 × diameter² ÷ 4 − post²) × depth, all in feet
Weight = bags × bag size
The site's general method is on our how we calculate concrete page.
| Mix | Bags In This Tool | Typical 28 Day | Main Use |
|---|---|---|---|
| Concrete Mix | 40 to 90 lb | 4,000 psi (27.5 MPa) | General structural uses |
| Fast-Setting | 50 and 60 lb | 4,000 psi (27.6 MPa) | Setting posts, with a final set in 20 to 40 minutes |
| 5000 | 50 to 80 lb | 5,000 psi (34.4 MPa) | High early strength, and colder weather |
| Crack-Resistant | 50 to 80 lb | 4,000 psi (27.5 MPa) | Reducing drying-shrinkage cracks |
All four sheets describe uses at 2 inches (50 mm) or thicker. The sheets list other sizes for some regions, such as Canadian kilo bags. They are not in this tool.
These counts include 10% extra. The thicknesses are examples, so follow your plans.
| Slab | Depth | 80 lb Bags | 60 lb Bags | 20 kg Bags |
|---|---|---|---|---|
| 10 × 10 ft | 4 in | 62 | 82 | 112 |
| 12 × 12 ft | 4 in | 88 | 118 | 161 |
| 20 × 10 ft | 4 in | 123 | 163 | 224 |
| 3 × 3 m | 100 mm | 59 | 78 | 107 |
| 4 × 3 m | 100 mm | 78 | 104 | 142 |
| 6 × 3 m | 100 mm | 117 | 156 | 213 |
The Concrete Mix sheet advises cutting control joints 1 inch (25 mm) deep every 6 to 8 ft (1.8 to 2.4 m). It also says to keep curing for 5 days in warm weather or 7 days in cooler weather. For a full slab list, use the concrete slab material calculator. Our slab thickness guide explains how thickness is chosen.
The number depends on the hole and the post. The Quikrete concrete calculator takes the square post off the round hole.
| Hole | Post | 50 lb Bags | 60 lb Bags | 20 kg Bags |
|---|---|---|---|---|
| 8 × 24 in deep | 3.5 in square | 2 | 2 | 2 |
| 10 × 24 in deep | 3.5 in square | 3 | 3 | 4 |
| 10 × 30 in deep | 3.5 in square | 4 | 3 | 4 |
| 12 × 36 in deep | 3.5 in square | 7 | 6 | 8 |
| 12 × 36 in deep | 5.5 in square | 6 | 5 | 6 |
| 16 × 36 in deep | 5.5 in square | 11 | 9 | 12 |
Counts are for one post, with 10% extra, rounded up. The Concrete Mix sheet says hole depth should be a third of the overall post height. The Fast-Setting sheet says to wait 4 hours before putting strain on a set post, and it uses about 1 gallon (3.8 L) of water per 50 lb bag for setting posts, depending on soil. In Australia, follow your fence or structure's own rules. The concrete post hole calculator gives metric counts, and Cement Australia's fence post guide covers local practice.
Each data sheet gives a starting and a maximum amount. Start low, since too much water weakens concrete. The tool shows a total range in litres, but it leaves water blank for the 60 lb Fast-Setting bag, because we did not find a figure for it.
| Bag | Concrete Mix Water | 5000 And Crack-Resistant Water |
|---|---|---|
| 40 lb | 1.4 to 2.1 L | Not listed |
| 50 lb | 1.7 to 2.6 L | About 1.8 to 3 L |
| 60 lb | 1.9 to 3.3 L | 2.1 to 3.5 L |
| 80 lb | 2.8 to 4.3 L | 2.8 to 4.7 L |
| 90 lb | 3.3 to 4.7 L | Not listed |
A Quikrete concrete calculator is only as good as the yield you give it. Before you trust any count, check these on the bag or data sheet:
Damaged, damp or old bags can behave badly, so check them before you start. Our earlier concrete bag calculator shows how published yields can differ even for one Australian brand.
In our November 2026 search, we didn't find standard Quikrete concrete bags listed by the big Australian hardware chains. The listings we saw were mostly online import sites, for smaller specialty products. Heavy bags are costly to ship, so an Australian bag is usually the practical choice. Availability can change, so ask your local store.
That's why the result always shows the same job in 20 kg bags and as a ready-mix order in m³. You can follow an American video's method and still buy local products.
American videos are handy for technique, but the numbers need care. Here is a safe way to use them with this Quikrete concrete calculator:
| American Size | Metric |
|---|---|
| 2 in slab minimum | 50.8 mm |
| 4 in slab | 101.6 mm |
| 6 in slab | 152.4 mm |
| 8 ft joint spacing | 2.44 m |
| 10 × 10 ft slab | 3.05 × 3.05 m |
| 4 × 4 post (actual 3.5 in) | 89 mm |
The 3.5 inch figure is the usual actual size of an American 4 × 4 post. Measure your own post, since Australian timber and steel sizes differ.
These products have a similar purpose. They are not the same mix, so read the label and don't assume the numbers match.
| If A Guide Says | Look For | Example |
|---|---|---|
| Concrete Mix | General purpose 20 kg premix | Cement Australia Concrete Mix |
| Fast-Setting | Rapid or fast set post mix | Dingo Fast Set Hi Strength |
| 5000 | Higher strength bag, with a stated MPa | Dingo Hi Strength |
A 20 kg bag is about 44 lb, and an 80 lb bag is 36.3 kg. Australian bags are lighter and easier to lift, so you need more of them. At our starting yield, one 80 lb Quikrete bag makes about the same as 1.8 × 20 kg bags. The concrete bag yield calculator helps when your bag lists a different yield.
American mixes are rated in psi. Australia uses MPa, and 1,000 psi is about 6.9 MPa. So 4,000 psi is about 27.6 MPa, and 5,000 psi is about 34.5 MPa. The data sheets round these slightly differently.
That doesn't make a bag an N25 or N32 mix. Australian grades come with their own testing and rules, and a site-mixed bag depends on water, mixing and curing. See concrete grades explained. If your plans name a grade, use a product or supplier that can meet it.
These match the Quikrete concrete calculator above. Each one includes 10% extra.
Holes are 10 inches across and 24 inches deep, with a 3.5 inch square post.
Bags suit small pours, but the work adds up fast, as any Quikrete concrete calculator will show. A cubic metre takes about 108 × 20 kg bags. iSeekPlant says most Australian suppliers want 3 to 4 m³ per delivery, with short load fees below that. So compare both once your job nears 1 m³. The concrete order calculator and concrete cost calculator can help.
Wet cement can burn skin, so wear gloves and boots. Bags are heavy, so lift with care or get help. Before digging, lodge a request with Before You Dig Australia, and read Safe Work Australia's silica guidance before you cut concrete.
Divide your volume in cubic feet by the bag's yield, add your extra, and round up. An 80 lb bag yields 0.60 cubic feet.
About 0.60 cubic feet, or 17 litres, according to the data sheet.
45, before any extra.
60, at a yield of 0.45 cubic feet per bag.
At 4 inches thick with 10% extra, about 62 × 80 lb bags.
About 6 to 9 pints (2.8 to 4.3 L) for Concrete Mix, starting at the low end.
The data sheet gives a final set of 20 to 40 minutes, and says to wait 4 hours before putting strain on a post.
The sheet gives typical strength of 4,000 psi, or 27.5 MPa, at 28 days.
We didn't find standard bags at the big Australian hardware chains in our November 2026 search. Ask your local store.
There is no exact match. Look for a 20 kg premix with a stated yield and MPa rating, and read the label.
About 1.8 at our starting yield of 0.0093 m³ per 20 kg bag.
The sheet lists slabs 2 inches or thicker, but you have far less working time, so plan the pour carefully.
No. This is an independent tool from ConcreteCreek, and it isn't affiliated with or endorsed by the maker of QUIKRETE products.
No. Your numbers stay in your browser and nothing is uploaded. Use Download Result PDF to keep a copy.
Figures reviewed November 2026. Sources: published QUIKRETE data sheets, Cement Australia, iSeekPlant and the other sources linked in the sections above. ConcreteCreek is independent and not affiliated with the maker of QUIKRETE products. Yields and products change, so check the label. Read our Disclaimer and Calculator Methodology.