How to calculate how much concrete is needed?

[PeteB8]

How much concrete mix or number of 20kg bags is required to cover an area of  2m long x 150mm deep x 400mm wide.

[J-TAC]

Here is a link for a concrete calculator that will do that for you, hope it helps

https://www.calculator.net/concrete-calculator.html

[MitchellMc]

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

[mike57]

how many bags of cement , sand and stones if mixing from scratch

[MitchellMc]

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

[azizsyed01]

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

[Jason]

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

[jainlal]

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.

[MitchellMc]

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
 

[jainlal]

Thanks Mate, will do that.