How much concrete mix or number of 20kg bags is required to cover an area of 2m long x 150mm deep x 400mm wide.
Here is a link for a concrete calculator that will do that for you, hope it helps
https://www.calculator.net/concrete-calculator.html
Welcome to the Bunnings Workshop community @PeteB8. It's sensational that you've joined us, and many thanks for your question about the number of concrete mix bags you'll need for your slab.
I apologise as I read your measurements incorrectly. I've now edited my response below to reflect the correct amount.
It's fantastic to see you've already received a helpful reply from @J-TAC. Here's another calculator from one of our suppliers using purely metric units. You'll require 14 x 20kg bags of concrete.
We look forward to hearing more about your concrete slab project. Please let us know if you have further questions or need assistance.
Mitchell
how many bags of cement , sand and stones if mixing from scratch
Welcome to the Bunnings Workshop community @mike57. It's great to have you join us and many thanks for your question about mixing concrete.The normal ratio for concrete is 1 part cement, 2 parts sand, and 3 parts gravel. So, for every bag of cement you'd need, you'll use two bags of sand and three bags of gravel.
What sort of project are you working on?
Please let us know if you need further assistance or have questions.Mitchell
hello
I’m going to do the concert slab of 3.5m x 3.5m it comes up to 1.22 Quebec m2 with 100mm thickness can anyone suggest me how much concrete mix does it requires and what is the easiest way to do. Suggestion are really appreciated thanks.
regards
Aziz
Welcome to the Bunnings Workshop community Aziz (@azizsyed01). We're pleased to have you join us and look forward to seeing you complete your concrete slab project.
Check out this helpful step-by-step guide by experienced Workshop member @tom_builds: How to pour a concrete slab. It should be really helpful to you.
The normal ratio for concrete is 1 part cement, 2 parts sand, and 3 parts gravel. So, for every bag of cement you'd need, you'll use two bags of sand and three bags of gravel. Here's a calculator from one of our suppliers that you can use to calculate how much is required.
Hope that helps get you started. Let us know if you have more specific questions. We're here to help.
Jason
Hi Mitch
Mate, using that concrete calculator for area [1.41m x 0.51m x 130mm] L X W X D repairing driveway cutout, it stated that i need least 11 x 20kg bags.
My question is based on what I've read in your previous reply to another customer, 1 Concrete, 2 Sand & 3 Gravel, how do you input those into this calculation [volume], do i divide these by factor 2 or 3 now as Sand and Gravel will take that volumetric space and say i will only need 4 bags now.
Welcome to the Bunnings Workshop community @jainlal. It's brilliant to have you join us, and many thanks for your question about concrete quantities and ratios.If you need eleven bags of concrete for the area, I suspect you'd be very close to needing two cement, four sand and six gravel for the same volume. However, for the sake of not having to run back to the store mid-pour, I'd grab three cement, five sand and seven gravel, just to be safe.Please let me know if you have any questions.Mitchell
Thanks Mate, will do that.
Hi team
complete newbie at concrete but first time a charm right lol
So I'm looking at a diy concrete slab.. bearing loading of about 3-5T for a carport out in the farms
5mx4mx100mm
i have the mesh and all, just need the maths for the mix and how to do smooth finish lol
how many cubic meters of premix 10mm and how many cement bag? In addition how many liter of water per 80L as that the volume of the mixer ? thanks
Welcome to the Bunnings Workshop community @mitc69. It's terrific to have you join us, and many thanks for your question about creating a concrete slab.A slab of that size would be a push to pour by hand. By the time you'd have mixed the bags and got them down, the area that you began with would be beginning to set. You'd need at least three friends: two on mixing and another to assist you with spreading. You're really at the point of something that's just not possible by hand. You could do it with an expansion gap down the middle. Mix and pour one half one day and the other the next.
On the maths, that is two cubic metres of concrete or 231 x 20kg bags of concrete. If you're following a typical concrete mix ratio of 1:2:4 (cement:sand:aggregate) then you'd need approximately 35 x bags of cement, 69 x bags of sand and 138 x bags of aggregate. It's going to require around 350L of water.
I strongly encourage you to consider having a slab of this size pumped or divided into manageable sections.
Here's a helpful guide: How to pour a concrete slab.Please let me know if you have any questions.Mitchell
Hi Mitchell
thanks for the maths, save me time to test and trail... I did get a quote but it was rather too high in that regard 😕
Unlike brissy I can't seem to find any concrete truck that ready to pump or is willing to come out to the farms hence the diy
And I'm planing to do section by section at this rate 🙂 and again much appreciated 🙂
Just some updates, not perfect but with some self level will be able to tile it later 🙂
massive 13x10x14mm slab once completed, then another 20x10 for the machines
first slab took about 13hrs solo, with good ozitio mixer !
and again thanks 🙂
Hi @mitc69,
A 20 square metre slab for your first foray into concreting is pretty brave and I have to say you've done a great job considering.
I bet your body was feeling it the morning after a 13-hour day of concreting.
Thank you for sharing.
Jacob
How many bags of concrete will I need for 4mx1m x 120mil deep
Thnx
What is the bag qty for 20kg bags
This is based on 60 an 80kg bags advise
Hello @MarioTedone
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about how many concrete bags you'll need for your concrete base.
To calculate how many 20kg bags of concrete you will need for your base, we start by determining the total volume of concrete required. The base dimensions are 4 meters long, 1 meter wide, and 120mm (0.12 meters) deep. To find the volume, multiply the length by the width and the depth: 4 × 1 × 0.12 = 0.48m cubic meter. This means the total volume of concrete required is 0.48 cubic meters.
Next, we need to determine how much volume a single 20kg bag of pre-mixed concrete can cover. Typically, a 20kg bag covers about 0.01 cubic meters of volume when mixed. This figure can vary slightly depending on the specific product, so it's worth checking the coverage information provided by the manufacturer of the concrete mix you’re using. Finally, we calculate the number of bags needed by dividing the total volume required by the volume covered by each bag. In this case, 0.48 ÷ 0.01 = 48.
Therefore, you will need approximately 48 bags of 20kg concrete to complete your base. It’s a good idea to purchase a couple of extra bags to account for any spillage, uneven levelling, or other unforeseen needs during the project.
However, if you your bag is 80kg you'll need to determine the coverage of an 80kg bag. Typically, an 80kg bag of pre-mixed concrete covers about 0.04 cubic meters when mixed. Dividing the total volume by the coverage per bag, 0.48 ÷ 0.04, shows that you’ll need 12 bags of 80kg concrete. To ensure you have enough for the project, it’s advisable to purchase one or two extra bags to allow for other unforeseen needs.
Please remember to wear personal protection such as gloves, goggles and a mask when working with concrete.
If you have any other questions we can help with, please let us know.
Eric
how many 20kg bags of concrete would I need for a concrete slab 6 metres x 2 metres. Thank you
Hi @gailando
I am going to assume a general purpose cement GP mixture for slabs for a shed floor or path and you will doing 70 mm - 100mm thickness ,
Cement 1 sand 2 Aggregate 3
Estimated 12 bags (70mm thick) you may need up to 3 bags more to finish the job. If you over order bunnings will refund fresh un damaged bags 🙂
I hope this is some SOLID advice.
Thank you so much for your advice. It has helped so much . I had no idea how to work it out. Once again thank you
Hi @gailando,
A warm welcome to the Bunnings Workshop community and thank you for your question.
For a 6x2m concrete slab that is 100mm thick, you need 1.2 cubic metres of concrete. In 20kg bags such as the one @Jewelleryrescue has mentioned, you would need 126 bags.
You can use this Concrete Calculator from our supplier Dingo Cement to confirm this.
Let me know if you have any further questions.
Wow , that is a big difference in the amount of bags needed from the previous answer. That is why I have been unable to work out the amount because everytime I tried to calculate I got different answers. Thank you so much for your assistance.
Hi @JacobZ
I think there is some thing wrong with those calculators I laid a slab close to 5 meters by 2 meter by 120mm on average. I had bought 80 Bags of 20 kg cement I used near half of them I had so many left over but used them in other projects. 4 car trips with 20 bags. Plus I did some extra slabs out of that lot and morter for bricks. and paver cement pads just tring to use it up.
My first random internet calculator also was around 126 bags for my job and this estimate for @gailando We might have used the same one.
I used another calculator and its saying 12x 20 kg bags so ???
Well I am still stumped at the estimate of 126 bags
Just checking my real usage.
For me is roughly 1 bag of cement per builders wheel barrow (1/2 a bag per mixer load, 2 mixer loads = fills the wheel barrow.)
So 126 bags makes 126 full builders wheel barrows thats alot of concrete, You also know what volume a builders wheel barrow can fill. now times 126 of them
A mental double check via material wieght.
So my weight estimate is Cement 1/2 bag is 10kg. sand 20 kg agg is 30kg so total 60 kg per mixer load. Double that is 120kg per wheel barrow load. well that checks out. 120kg per builders barrow load is a close reality you know this when you have to push it many times.
So approx it took me 20 wheel barrows to fill 5mx2m x 0.12 or 1.2 m cubed thats 20 to 30 bags of GP cement that is being generous
This is doing my head in lol.
My conclusion is buy 40 bags of cement and buy more at need. And by the end you will just need a few extras if al all.
Hi @Jewelleryrescue and @gailando,
The equation for calculating the volume of concrete is fairly simple as it is just a volume calculation.
Volume=6m×2m×0.1m
Volume=1.2m3
I think the issue we're having, which I missed in my previous response, is that Jewelleryrescue is referring to cement as opposed to concrete.
Cement, such as this Bastion 20kg General Purpose Cement, is a powder made from heated and crushed limestone and clay. When mixed with water, it hardens and sticks to other materials, acting as a glue. It’s mostly used in construction as part of mixtures, like concrete or mortar.
Concrete, such as this Bastion 20kg Concrete Mix, which I was referring to in my previous response, is a mixture of cement, sand and aggregate that can be mixed with water and used with no other additives.
The difference is that concrete is already mixed, whereas cement needs to be mixed with sand and aggregate to make it into concrete.
If you were using cement, like Jewelleryrescue's calculations are based on, you would need to add the sand and cement to the mix. A standard mixing ratio for concrete is 1:2:3, 1 part cement, 2 parts sand and 3 parts aggregate.
As a bag of cement is roughly 0.01m3, when mixed with sand and aggregate, a single bag of cement will make 0.06m3 of concrete. This means you would need 20 bags of cement, 40 bags of sand and 60 bags of aggregate to make up the 1.2m3. The sum of these materials equals 120 bags total. With 5% extra for mishaps, 1 bag cement, 2 bags sand and 3 bags aggregate, this makes your 126 bags of concrete.
I hope this has clarified. If not, please let me know and I'll try to explain further.
That explains the calculation differences thanks for that I should have seen it myself but a am always in learning mode open to better ways and ideas that really work.
Thanks for longer descriptions of the dual sets of calculations.
a slab of concrete 1.3mX600mmX150mm
how many bags of concrete mix do I need?
Welcome to the Bunnings Workshop community @emmjan. It's sensational to have you join us, and many thanks for your question about calculating concrete bags requirements.This is likely a one-off, but for the benefit of other readers coming across this discussion, you can find a variety of helpful calculation tools on the Cement Austalia website. You would need 0.117 cubic metres, which is 14 x 20kg bags of concrete.
You might also like to check out this helpful step-by-step guide: How to pour a concrete slab.Please let me know if you have any questions.Mitchell
Welcome to the Bunnings Workshop community @suzana. It's wonderful to have you join us, and many thanks for your question about concrete calculations.I apologise but we would also need to know the depth of the slab in order to calculate how much premixed concrete you will need. For example, a 3m x 6m slab at 100mm thick has a volume of 1.8 cubic metres. On average, you would need around 100 x 20kg bags of premixed concrete to make 1 cubic metre, so for this slab you would be looking at about 180 bags.
If your slab is intended to be thicker or thinner, the amount will change, so let us know the depth you are planning and we can work out a more accurate figure for you.Please let me know if you have any questions.Mitchell
