a way to know how much glass left in the roll

its a silly question but does anybody came up with a way to calculate how much glass is in the roll?
I forgot to track my current roll and I have no Idea how much glass I have and unfortuently I need to wait about a month from the moment I order the the fiberglass till it reaches to me.
so if anyone have a way/idea ill be glad to hear it.

Sorry man; The only for sure way to know is to count it as you take it off the roll. A lot of guys in pro glass shops have tracked the # of yards and boards for so long that they can look at the diameter of the yardage still on the roll and tell you what’s left. I think you better go ahead and order. Best to have it when you need it and not run out. Next time count it. Or at least keep track of how many boards you average per roll.

It can be seen as a math problem…straight up density stuff:
Weigh an empty core, weigh the roll you have, weigh a scrap piece of cloth from that roll.
-Take the difference of roll you have minus empty core = weight of glass
-Take the weight of the scrap divided by area of scrap= density of glass
-Take the weight of glass divided by density of glass=square units of glass
-Take square units divided by width of glass=linear units=what’s left on the roll

Or just unroll it and measure…fast, easy, way less chance for computational error. Use a second core and have someone to help roll and keep it neat.

jrandy’s last part is your best bet. Roll it out, measure as you go, take it up on another roll/core.

Odds are, no matter what you have, it’s 2" too short. Lol

That’s what she said !

Plan ahead…order early. It doesn’t go bad.

Quick guesstimate, measure thickness of cloth on roll. Calculate ‘average diameter’ of cloth (outer cloth diam + inner cloth diam divided by 2).
Divide total thickness of cloth on roll by thickness of cloth (4-oz, 6-oz, etc.) and multiply by the cloth “average diameter,” then multiply that result by 3.1416 (Pi). Measured in inches, answer is in inches.
E-Glass Thickness
4-oz = 0.0059"
6-oz = 0.0093"
At best, this is a quick “guesstimate.” If you calculate you have enough for three more boards, I would not count on having enough for more than 2 boards.
If the cloth is “loosely wrapped” around the cardboard tube, this method will not be very accurate.
Safest bet, order another roll of cloth.

Leave it to stone burner to complicate the shit out of it.

She said give me 12 oz cloth and make it hurt. So I gave her 2 layers of 6 oz and punched her in the nose.

Dude, the rule of thumb is: if you look at a roll of cloth and don’t see a boards worth of cloth, then you need to reorder.

Don’t complicate it with math and scales. Just unroll it and measure it.

A ruler, thickness and circumference of a circle.
One minute of simple Middle School math.

For Old-Shoolers, one minute of simple High School math.

When I was in middle school there was no such thing as middle school. We weren’t working on circumferences until high school geometry. I guess that’s why I like surfing so much. No math!!! LOL

A long time ago, they called 7th and 8th grade Junior High. I did geometry and circumferences as a sophomore in High School.
Before High School, it was Middle School that my kids attended. In Middle School, they were way ahead of what I did in Junior High.

Different manufacturers of glass, flat weave 6 oz s cloth, regular E cloth. How hard the machine winds the cloth, etc, etc. A man of your advanced math skilz would know this…anyone that has used a roll of fiberglass would know they are all different. But then any one who has actually made a surfboard or two would know this…

I will make it easier to understand, go down the toilet paper isle in your favorite Piggy Wiggly, look at the TP… Look at your favorite brand " the one that doesn’t knock your hemroids Out of alignment" notice the circumference, and notice the weight, notice the stated yards. Now do your math formula…only works if you are buying you antihemroid Charmin…not so good for your Piggly Wiggly sand paper.

Show us the boards?

No need to discuss why one method is better than the other.
People are just trying to help so that the poster can use the method he prefers.

If you don’t mind to unroll the roll, why not, that’s very accurate!
If you have some scales available, why not use them?
If you understand math done by 12 year olds, why not use it?


  1. roughly calculate or judge the value, number, quantity, or extent of.

You could probably pull a thread along the edge and measure it’s length.