# How much does one cubic FOOT of concrete weigh? **URL:** \ **Category:** Factual Questions\ **Created:** [June 25, 2005, 8:23pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827 "2005-06-25T20:23:20Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Carnac\_the\_Magnificent](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Carnac\_the\_Magnificent](https://boards.straightdope.com/u/Carnac_the_Magnificent)\ **Post date:** [June 25, 2005, 8:23pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/1 "2005-06-25T20:23:20Z")
A contractor is delivering freshly mixed concrete to a friend’s house for repair work. This friend is curious re: how much 1 cubic FOOT on liquid concrete weighs, allowing for variances in mixes. I guessed somewhere in the 100-pound range. Any ideas? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 25, 2005, 8:36pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/2 "2005-06-25T20:36:55Z")
Some numbers [here](http://hypertextbook.com/facts/1999/KatrinaJones.shtml). You can use Google to convert between units ([example](http://www.google.com/search?q=1000+kg%2Fm%5E3+to+lb%2Ffoot%5E3)). ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [June 25, 2005, 8:37pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/3 "2005-06-25T20:37:40Z")
Not a bad guess. [140 - 150](http://www.reade.com/Particle_Briefings/spec_gra2.html) would be better. ---
**Author:** ![Carnac\_the\_Magnificent](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Carnac\_the\_Magnificent](https://boards.straightdope.com/u/Carnac_the_Magnificent)\ **Post date:** [June 25, 2005, 9:30pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/4 "2005-06-25T21:30:35Z")
> [@Tapioca Dextrin](#): > > Not a bad guess. [140 - 150](http://www.reade.com/Particle_Briefings/spec_gra2.html) would be better. whoops. I should note it will be poured from a cement mixer. The chart you link speaks of cement in a “slurry” form, giving a weight of 90 pounds per sq ft. Would that be the correct term/weight? ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [June 26, 2005, 1:29am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/5 "2005-06-26T01:29:11Z")
From my concrete mixer driving days I was told that a cubic yard of concrete weighs just short of a ton. Just divide a ton by 27 for an aproximate amswer. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [June 26, 2005, 5:09am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/6 "2005-06-26T05:09:15Z")
> [@justwannano](#): > > From my concrete mixer driving days I was told that a cubic yard of concrete weighs just short of a ton. > Just divide a ton by 27 for an aproximate amswer. That’s just a little more than water weighs–you put a lot of rocks in it, it’s going to weigh more ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [June 26, 2005, 5:23am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/7 "2005-06-26T05:23:17Z")
Solid rock runs 140 to 180 lbs. per cubic foot, depending on what type of rock. (Excluding the rare ones like pure gypsum, or Galena) While concrete will be variable, depending on what you use as an aggregate, it should be in the same range. So, 150 lbs. for a cubic foot seems entirely reasonable. ## Tris “It is when I struggle to be brief that I become obscure.” ~ Horace ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [June 26, 2005, 6:32am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/8 "2005-06-26T06:32:54Z")
> [@RM Mentock](#): > > That’s just a little more than water weighs–you put a lot of rocks in it, it’s going to weigh more No. Water is extremely dense and non compressible. If you substitute volume x of water with an equal volume of rock, the weight will likely go down, as rock is not as dense as water. Put a brick in a pan of water and watch how much water it absorbs via capillary action. ---
**Author:** ![Jman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jman/32/4416_2.png) [@Jman](https://boards.straightdope.com/u/Jman)\ **Post date:** [June 26, 2005, 6:38am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/9 "2005-06-26T06:38:17Z")
> [@danceswithcats](#): > > No. Water is extremely dense and non compressible. If you substitute volume x of water with an equal volume of rock, the weight will likely go down, as rock is not as dense as water. Put a brick in a pan of water and watch how much water it absorbs via capillary action. Rock is not as dense as water? Oh…so that explains all the floating rocks in my lake. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [June 26, 2005, 6:48am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/10 "2005-06-26T06:48:09Z")
> [@danceswithcats](#): > > rock is not as dense as water. ?? your average sex rock is two and a half times more dense than water ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [June 26, 2005, 7:17am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/11 "2005-06-26T07:17:47Z")
> [@Jman](#): > > Rock is not as dense as water? Oh…so that explains all the floating rocks in my lake. Well, maybe all the rocks around his place are pumice. I took my son and some friends up to reservoir on the Los Angeles aqueduct near Bishop one time. One of them idly picked up a rock and threw it in the lake and the rock floated. They had a great time throwing the floating rocks in the water. ---
**Author:** ![Can\_Handle\_the\_Truth](https://avatars.discourse-cdn.com/v4/letter/c/6a8cbe/32.png) [@Can\_Handle\_the\_Truth](https://boards.straightdope.com/u/Can_Handle_the_Truth)\ **Post date:** [June 26, 2005, 7:36pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/12 "2005-06-26T19:36:38Z")
Architectural designer/engineer weighing in. In my structural calculations I use 150 lbs per cubic foot for concrete. ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [June 27, 2005, 5:25am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/13 "2005-06-27T05:25:19Z")
> [@RM Mentock](#): > > That’s just a little more than water weighs–you put a lot of rocks in it, it’s going to weigh more Water weighs 8 pounds per gallon. I think you have the decimal in the wrong place. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [June 27, 2005, 5:46am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/14 "2005-06-27T05:46:31Z")
> [@justwannano](#): > > Water weighs 8 pounds per gallon. > I think you have the decimal in the wrong place. And there’s a factor of about 8 gallons per cubic foot ---
**Author:** ![Waterman](https://avatars.discourse-cdn.com/v4/letter/w/b2d939/32.png) [@Waterman](https://boards.straightdope.com/u/Waterman)\ **Post date:** [June 27, 2005, 6:37am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/15 "2005-06-27T06:37:18Z")
Water weighs 8.34 pounds per gallon and there are 7.48 gallons per cubic foot, therefore water weighs 62.4 pounds per cubic foot at normal temperatures (~60 - 80 degrees F). An individual rock (or other mineral matter) has a density greater than that of water, however, it’s bulk density will be less because of void volume. If the previously stated number of one ton per cubic yard then concrete would weight ~ 74.7 pounds per cubic foot which is too low. I checked it out and here’s a link to site where the value is given as 135 - 142 pounds per cubic foot depending on the admixture and aggregates used. [Weight of a Cubic Foot of Concrete](http://www.submarine.freehosting.net/resources.html) ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [June 27, 2005, 6:39am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/16 "2005-06-27T06:39:48Z")
> [@Can Handle the Truth](#): > > Architectural designer/engineer weighing in. > > In my structural calculations I use 150 lbs per cubic foot for concrete. Sounds about right. Fresh water weights 62.4 lb./ft[sup]3[/sup] and 2.5 times that is 156. ---
**Author:** ![NillyWilly](https://avatars.discourse-cdn.com/v4/letter/n/3da27b/32.png) [@NillyWilly](https://boards.straightdope.com/u/NillyWilly)\ **Post date:** [June 27, 2005, 8:45am UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/17 "2005-06-27T08:45:26Z")
**danceswithcats** If rock is not as dense as water, all rock would float. ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [June 27, 2005, 5:27pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/18 "2005-06-27T17:27:23Z")
Well it appears I’m wrong. From Truck Mixer Driver"s Manual May 1995 National Ready Mixed Concrete Association The purpose of the unit weight is to find the weight of 1 cubic foot of concrete. Unit weight is measured in pounds of concrete per cubic foot,which is abberviated lb./cu.ft. Expect concrete to have a unit weight of 140 to 150 lb./cu.ft. Comcrete made with lightweight aggreates will have a unit weight of 115 to 125 lb./cu.ft. I always thought that guy was blowing smoke most of the time anyway. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 27, 2005, 6:02pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/19 "2005-06-27T18:02:04Z")
> [@RM Mentock](#): > > ?? your average sex rock is two and a half times more dense than water A _what_ rock? 😕 ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [June 27, 2005, 7:00pm UTC](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827/20 "2005-06-27T19:00:50Z")
any old fucking rock [Next page](https://boards.straightdope.com/t/how-much-does-one-cubic-foot-of-concrete-weigh/309827.md?page=2)