Concrete Bag Calculator

About Concrete Bag Calculator

Concrete Bag Calculator converts the dimensions of your pour into a bag count for the four most common pre mixed concrete bag sizes. The yields it uses are the standard ones: a 25 kg bag makes about 0.012 m3, a 40 kg bag about 0.020 m3, a 60 lb bag about 0.45 cubic feet and an 80 lb bag about 0.60 cubic feet. That works out to roughly 84 bags of 25 kg or 50 bags of 40 kg per cubic metre, and 60 bags of 60 lb or 45 bags of 80 lb per cubic yard. All four counts are shown together so you can compare what your supplier actually stocks, and every count is rounded up because a part bag will not finish a pour. Bag counts climb faster than most people expect, which is exactly why this figure is worth checking before buying: a project needing 2 m3 is nearly 170 bags of 25 kg mix, well past the point where a ready mix delivery is cheaper and dramatically less work.

How to use Concrete Bag Calculator

  1. Choose metric or imperial input
  2. Enter length, width, and depth of your slab
  3. See volume and bag count in both metric and imperial instantly

Frequently Asked Questions

How many bags of concrete do I need?
Work out the volume of your pour, add a waste allowance, then divide by the yield of one bag. Per cubic metre you need about 84 bags of 25 kg or 50 bags of 40 kg. Per cubic yard you need about 60 bags of 60 lb or 45 bags of 80 lb. Enter your dimensions above to get all four counts at once.
How much concrete does one bag make?
A 25 kg bag yields about 0.012 m3, a 40 kg bag about 0.020 m3, a 60 lb bag about 0.45 cubic feet and an 80 lb bag about 0.60 cubic feet. These are standard values for pre mixed concrete and can vary slightly between brands, so check the yield printed on the bag.
At what point should I switch from bags to ready mix?
Around 1 to 1.5 m3, or roughly 1.5 to 2 cubic yards. Below that, bags avoid the minimum load fee that ready mix suppliers charge. Above it, you are mixing well over 100 bags, and a delivery is normally cheaper per cubic metre as well as far faster.
Why are bag counts always rounded up?
Because a partial bag cannot complete a pour. The calculator rounds every count up to the next whole bag, and the waste percentage is applied to the volume before that rounding, so the count already includes your buffer.
Is a 40 kg bag better value than a 25 kg bag?
Usually yes per cubic metre, since 50 bags of 40 kg cover the same volume as 84 bags of 25 kg. The trade off is handling weight: 40 kg bags are harder to lift and carry, which matters if you are working alone or moving them any distance.

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