You are watching: How many cubic feet in a 80lb bag of concrete

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## How to Calculate exactly how Much Concrete i Need

The an initial thing you should do is relax. It yes, really ain’t that hard. Don’t let terms favor “cubic feet” and also “yield” and also “density” bother you. There are basically 2 steps. The an initial step is figuring the volume that the an are you desire to fill. It no make any type of difference if you want to fill it with concrete or vanilla ice cream cream. Volume is volume. Because of the amount of concrete required for most work it is usually simplest to figure the volume in cubic feet. If your job is huge enough to calculate the volume in cubic yards rather of feet, call a prepared mix concrete truck. Once you hear “cubic” think ice cream cube. An ice cube usually has actually three sides (at least the ones you do in the trays in your freezer at residence do). The method to discover the volume the a cube is come multiple all 3 sides. If her cube were a perfect cube and also it to be 2 feet wide and 2 feet long and 2 feet deep, the volume would be 8 cubic feet. Concrete slabs room usually no perfect cubes for this reason the mathematics is a small different. If you were going to pour a slab the was 2 feet wide and 2 feet lengthy it would certainly not likely be 2 feet deep. It might be 4” deep which is a common depth because that a concrete slab. So currently the equation looks prefer this: 2’ x 2’x 4”. The problem is you have to get whatever into the exact same units; you can not multiple feet by inches. This is wherein folks gain hung up yet it’s actually fairly easy. Just multiple 2 x 2 x 4 ÷ 12. The prize is 1.3 cubic feet.

If you room filling a round hole in the soil to set a write-up or mail box, the calculation because that volume is different than a cube or rectangle. The formula for the volume of a round hole is *pi r2 *x depth. Or 3.14 x radius x radius x depth. The radius is fifty percent the broad of the hole. Uneven you space doing a monster hole it can be most basic to execute this all in inches. If your hole is 36” deep and also 10” wide, the calculation is 3.14 x 5 x 5 x 36 ÷ 1728. This provides you 1.6 cubic feet. If girlfriend forget the 1728 it is merely 12” x 12” x 12” or the variety of cubic inches in a cubic foot.

So currently that we know the volume the 2nd step is to calculation how many bags that concrete that will require to fill the hole. On the bag it will tell girlfriend how many cubic feet the bag will fill. This is the “yield”. The productivity on one 80 lb bag is about 6/10 (.6) cubic feet. If you take the example above of 1.6 cubic feet, the calculation would be :

1.6 ÷ .6. = 2.7 bags

If you happen to it is in enthralled through math calculations I administer the complying with information on exactly how to calculate the yield the I claimed was .6 cubic feet because that an 80 lb bag. The an initial thing you need to understand is the “density” of the concrete. If I offer you a crate filled with concrete that measures 12” x 12” x 12” (or 1 cubic foot), exactly how much execute you think it will certainly weight? walk ahead and also take a guess- practically everyone it s okay it wrong. The prize is 145 lbs. (If it to be filled through beer it would weigh 64 lbs.) This method the “density” the concrete is around 145 lbs every cubic foot. Currently that we have actually that details we deserve to calculate the yield. Add up both the dry product in the bag (80 lbs) and also the water the takes come mix it increase (1 gallon i m sorry weighs 8.3 lbs) because that a complete weight of 88.3 lbs. Then divide the full weight by the thickness of the concrete.

88 ÷ 145 = .60 cubic feet.

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There is one technique for calculating the variety of bags required which is even easier. Us have already done the math for friend on concrete as well as a number of other products. Visit our calculators page prior to your next project. Determine just how much you require from home, the save aisle or indigenous the jobsite.