Measuring film: find the roll length of used roll using ruler to measure its radius

[Selv]

Hi all I am new so I am unsure which forum to post my question in.

I work in a warehouse and do stock counts a lot. I need to measure rolls of film. I know the dimensions of a full roll and the total length of the roll.
What I want to do is find the roll length of a used roll using a ruler to measure its radius.
Is this possible? If so can someone help me with a formula???
I currently use the roll weight to work out roll length comparing to a new roll, but some rolls are too heavy to weigh.
Any help is greatly appreciated.
And sorry again if I have posted this in the wrong forum

 

[Deleted member 4993]

Hi all I am new so I am unsure which forum to post my question in.

I work in a warehouse and do stock counts a lot. I need to measure rolls of film. I know the dimensions of a full roll and the total length of the roll.
What I want to do is find the roll length of a used roll using a ruler to measure its radius.
Is this possible? If so can someone help me with a formula???
I currently use the roll weight to work out roll length comparing to a new roll, but some rolls are too heavy to weigh.
Any help is greatly appreciated.
And sorry again if I have posted this in the wrong forum

These calculations - although simple - will need calculator (because you'll need to calculate square root of numbers).

In addition, calculation of length through measuring diameter will involve several assumptions - thus will not be as accurate as the weight method.

 

[stapel]

I work in a warehouse and do stock counts a lot. I need to measure rolls of film. I know the dimensions of a full roll and the total length of the roll. What I want to do is find the roll length of a used roll using a ruler to measure its radius.

Is this possible? If so can someone help me with a formula?

The formula (in particular, the complexity thereof) will vary with whatever you've been given in class (or, if this is actually from "real life", depends on how specific you want to get).

I currently use the roll weight to work out roll length comparing to a new roll, but some rolls are too heavy to weigh.

Actually, a weight-based measurement is probably more accurate (depending upon the accuracy of the scale being used) that a radius-length-based measure, as the latter would also need you to quantify the "tightness" of the roll, too (or else you'd need to handle the possibly-frail celluloid yourself, to tighten things up around the spindle).

You could use a crude formula, such as is given here. Or you could get technical, such as the derived formula here. Or, if your class has given you something to use, use that instead.