The Origami Forum

A sort of math problem for you gals/guys: I bought a roll of 3,000 cm of paper. It's 70 g/m² paper. I have used some of it. That's why the roll is currently 1.1 cm thick, but I don't know how thick it was when I bought it. Can you please give me an estimate of how many centimeters I have left of the 300 I bought?

I know I don't give you all the needed data, but maybe the data here and your experience with your own paper rolls can help you with the math problem. I need to know if I have enough paper for a big project and this is the last roll of this kind of paper in my country ! That's why it's important for me to know if it's enough.

Thanks in advance .

EDIT: I had the length wrong, so I fixed it.

How thick was the roll when you started, and how much of the roll is empty/taken by a cardboard tube?

it would also help if you have the width of the paper (in microns, i think they usually list it?) since gsm is a measure of density, and doesn't always correspond to thickness

Weigh the roll, find an estimate for the weight of the core and subtract? With the weight of the paper, it'll be easy to determine how many square meters you have, and then how much paper

A lot depends on how tightly the roll is coiled as well. Depending on the thickness of the paper in question, I’d imagine you wouldn’t have more than 40-50cm left—and that’s a fairly generous estimate.

The easiest way would be to unroll it and measure since it’s essentially impossible to tell with the information you’ve provided.
As DoubleTissue said above, you could weigh the remainder of the roll if you know its width. Divide the roll’s weight (in grams) by 70, and then divide by the width of the roll; that should give you a good idea of how much you have left.

That would work. As Baltorigamist said, it's definitely going to be easiest to unroll. If you had the original diameter, and the diameter of the inner gap, you could get the area the full roll took up in cross section (like a donut), and the cross-sectional area now, and use ratios to estimate how much is left.

Thank you everyone. I don't know how thick the roll was when I bought it; didn't measure it back then. The tube inside is around 2 mm thick and the hole inside the tube has a 4.9 cm diameter. The roll doesn't say the paper thickness, just the density. I'm sure I can weight the paper, but not the tube inside. How much must it weight? I can't unroll it because it's too much paper.

I appreciate your replies .

Come on 300cm what equals 3 meters with something missing already is too much to unroll? Are you sure you don't mean 3000cm equalling 30 meters?

I did... thank you for noticing that origami_8. The roll was originally 3,000 cm long. I'll edit the original post.

Haha we still dont have enough info.
If you weighed the whole thing that would help though! Could take an estimate for the cardboard tube weight and then solve for something in the range of the actual length

Everything weighs 1.5 Kg. How much do you think the cardboard tube weighs? The paper roll, and also the tube, are 70 cm tall.