Finding square feet ?


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Old 03-13-24, 12:25 PM
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Finding square feet ?

I have a cardboard box I want to waterproof, so I need to know the square feet to know how much waterproofing spray to buy. I tried Google, and two librarians at two different public libraries...and have three different numbers...756, 968, & 3792 sq ft. Math was never my forte (and apparently also not taught at librarian school), but I'm pretty sure neither of these answers are anywhere near correct!

If anyone here is any better at it, I need to know the square feet of a box 36"x21"x20".

Thanks for any help.
 

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03-13-24, 01:09 PM
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You have two sides of each dimension of 36 x 20, 36 X 21 and 20 X 21 inches.

2 x 36 x 20 = 1,440
2 x 36 x 21 = 1,512
2 x 20 x 21 = 840

1440+1512+840 = 3,792 square inches

3,792 / 144 (# sq inches in a sq foot) = 26.33 square feet
 
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Old 03-13-24, 12:49 PM
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If the box had six sides that were each 36"x36" that would be nine square feet per side.
So 6 x 9 = 54 square feet..... maximum. It would actually be less.

I believe for a 100% accurate number you would need to compute each side separately.
Actually that would be 2x one side, 2x other side, 2x top and bottom.

 

Last edited by PJmax; 03-13-24 at 01:06 PM.
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Old 03-13-24, 01:09 PM
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You have two sides of each dimension of 36 x 20, 36 X 21 and 20 X 21 inches.

2 x 36 x 20 = 1,440
2 x 36 x 21 = 1,512
2 x 20 x 21 = 840

1440+1512+840 = 3,792 square inches

3,792 / 144 (# sq inches in a sq foot) = 26.33 square feet
 
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Old 03-13-24, 03:55 PM
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Old 03-14-24, 04:46 AM
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Your first post contains the correct number (3792), but the wrong units. Was the units (sq. ft.) in the post provided by the device doing the calculation or you?
 
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Old 03-14-24, 12:51 PM
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I suppose it depends on how much water proofing you expect. Are you including the top and both inside and outside?
 
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Old 03-14-24, 01:05 PM
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Inside and outside... good point. If so, that would be 26.33 square feet x 2.
 
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Old 03-14-24, 03:16 PM
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Wouldn't it be easier, and probably more waterproof, to get a plastic box of similar size?
 
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Old 03-14-24, 04:55 PM
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I suspect that the "box" was an example and not necessarily a real problem. But I may be wrong!
 
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Old 03-15-24, 11:06 AM
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Math was never my forte (and apparently also not taught at librarian school)
Yes, I think you are right, I believe library science study does not require math courses. I believe they learn a lot though about research and information management.
 
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Old 03-15-24, 11:47 AM
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Nope, the box is the problem, and the measurements given are those printed on the box. Until I can find someone to make a similar size box out of plywood, for a reasonable price (not holding my breath), I'm gonna go for a temporary alleycat shelter of cardboard, which is within my ability to make. Been watching Youtube videos on how to waterproof a cardboad box, and starting to acquire the supplies. I figure on treating the inside with 'Krylon Sealer Clear', after I fill up any holes/joints with Flex Glue Clear. I have a quart of Liquid Rubber for the outside, and if that don't cover it, I have 3M Super 77 and a heavyweight garbage bag as backup.

The plastic boxes and insulated coolers at Walmart were twice as expensive as the cardboard box ($18), plus the trouble of cutting a door in them. I looked into masonite, but paying Lowes $79 to deliver a $30 order was not to my liking. If a 36" square box has 54 square feet, then 26.33 square feet (as a guess),seems more reasonable to me...I'll give it a try. Thanks to all.
 
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Old 03-15-24, 12:36 PM
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3792 sq/ft? Thats a big cardboard box. He must have got it at a big box store.

P.S. Woops! Didn't see the box dimensions at first.
 
 

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