# Estimating how many blocks

• posted on July 5, 2004, 12:56 am
Any one out there know the formula for figuring out how many cement blocks are needed to build a wall? Height X length divided by ???
Thanks for any help. Muff
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• posted on July 5, 2004, 1:03 am
Muff wrote:

Did you not pay attention during the 7th grade word problems?
If you want 10' long and 5' high, and you're blocks are 1' long (that would be 10 in a row) and 0.5' high (20 blocks high)... well, go find a 13 year old for this.
(and if you're offsetting them (ala a brick wall) you'll want some spares.)
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• posted on July 5, 2004, 3:47 am
No shit sherlock....except my blocks are 7 5/8 by 7 5/8 x 15 5/8. Now lay your 7th grade math on that one, asshole. Muff
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• posted on July 5, 2004, 4:10 am

And do you think that those odd dimensions are by accident? With the addition of mortar those blocks will effectively measure 8 x 8 x 16.
So figure out how tall you want to make the wall in inches and then divide by 8. This gives you the number of rows you'll need.
Now take the length of your desired wall in inches and divide by 16. This will give you the number if blocks needed per row.
Multiply the number of rows by the number of blocks per row to get a lower limit for the number of blocks you need.
Finally add in an extra block for every other row if you'll be staggering them.
Now add in some more blocks to handle oops and mistakes.
If you have problems with understanding this, then I suspect that you should hire a professional to build your wall.
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• posted on July 5, 2004, 4:57 am
Thanks for your inches theory. And yes I know about the 8X8X16 but all I wanted was the figure that Greg provided, Reason is that I need to order the blocks for the mexican that is going to lay the blocks amnd I wanted to make sure I ordered the correct number. And I dd not want someone else to make the order and have half of the load shipped some place else and me paying what the invoice said. I wanted to know how many blocks it would take to do the job. Muff
PS: Thanks Greg you are the only one who helped answer my question.
wrote:

And do you think that those odd dimensions are by accident? With the addition of mortar those blocks will effectively measure 8 x 8 x 16.
So figure out how tall you want to make the wall in inches and then divide by 8. This gives you the number of rows you'll need.
Now take the length of your desired wall in inches and divide by 16. This will give you the number if blocks needed per row.
Multiply the number of rows by the number of blocks per row to get a lower limit for the number of blocks you need.
Finally add in an extra block for every other row if you'll be staggering them.
Now add in some more blocks to handle oops and mistakes.
If you have problems with understanding this, then I suspect that you should hire a professional to build your wall.
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• posted on July 5, 2004, 2:21 pm
wrote:

And just what was wrong with John's answer? Don't forget Greg's including figuring deductions for doors/windows if there are any.
Harry K
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• posted on July 5, 2004, 4:29 am

blocks
im pretty sure most 7th graders have learned fractions. in any case if you cant figure out how many blocks, how do you expect to construct a wall? no, seriously....
randy
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• posted on July 5, 2004, 5:57 am
Actually that's easy because the 5/8" in those diminsions assumes a 3/8 grout between block, so actually they lay 8 inches high by 16 inches long. So divide the length of the wall in inches by 16 and the height of the wall in inches by 8. E.g., 20 feet long and 7 feet high is 240 inches by 84 inches. 240 divided by 16  blocks and 84 divided by 10.5, so you need 15 x10 0 blocks plus 15 x.5 half height block or fill in that space with wood. As in this case when division by 16 or 8 doesn't result in whole numbers, you will have to use frational height or lenght block in one row or make the amount in wood or steel.
Muff wrote:

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• posted on July 5, 2004, 1:28 pm
On Sun, 4 Jul 2004 23:47:38 -0400, "Muff"

When I was in 7th grade I would have rounded to 8x16 & determined that a block was 128 square inches. Then I'd measure the room in inches & divide by 128.
I'd remember seeing that my dad broke a few & that some extras were needed to overlap at the ends.
Since they were only about a quarter then, I'd just add 25-30 blocks to my previous answer. [they're a little over a dollar now but if you need another 10 blocks-- you better hope you have a truck to get them in-- they weigh 35pounds apiece]
What's your blocklayer's address? I think we should warn him that you're not too good with numbers & he better insist on cash.
Jim
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• posted on July 5, 2004, 5:00 pm
On Sun, 4 Jul 2004 23:47:38 -0400, "Muff"

Fractions were in 7th grade. :)
And it's 8 x 16, for standard block. The balance is the mortar joint. Divide the width in inches by 16, round up. Divide height in inches by 8, round up. Multiply the two together and add 10% for waste. Or multiply your total by 1.1 if you haven't done percentages yet in your math classes...
Jeff
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• posted on July 5, 2004, 3:46 am
Area in square feet times 1.125 plus whatever waste you have, assuming you use standard building units (8x8x16). If you make your walls, windows, doors in dimensions that are divisible by 8" you will minimize waste. They also make blocks in 4", 6" and 12" so with some planning you will seldom have to cut one as long as you stay on 2" increments.
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• posted on July 5, 2004, 3:53 am
Thanks, Greg, thats the figure I was looking for. Muff
Area in square feet times 1.125 plus whatever waste you have, assuming you use standard building units (8x8x16). If you make your walls, windows, doors in dimensions that are divisible by 8" you will minimize waste. They also make blocks in 4", 6" and 12" so with some planning you will seldom have to cut one as long as you stay on 2" increments.