![Image](https://media.steelroofsheets.co.uk/cache/a8/95/a895d2f1e4b7e5d0f115da8b5c087b0c.jpg)
https://www.steelroofsheets.co.uk/products/20mm-x-9mm-grey-self-adhesive-pvc-foam-tape-8m-roll/
I've been sent a roll of adhesive foam tape similar to the above (but not that one). It's a gift and I'm not sure how long it is, and prefer to measure its length myself and just email back a grateful "Thanks! That's great!" rather than a question about it. Of course I could stretch it out, measure it, and then rewind it before putting it in the cupboard for later use, but being adhesive backed that risks all sorts of hassles, from it falling onto the floor and picking up carpet fluff to personal entanglement, as well as possibly weakening the adhesive.
So instead, measuring the roll itself as is, the diameter across the whole disc is 20cms.
The diameter of the outside of the inner plastic ring (i.e. the diameter of the inside of the foam roll itself) is 8cms.
Counting from the outside one to the inside one, there are 10 "rings" (not actually rings of course) of tape.
So, my rough-and-ready take on it (not going for massive accuracy here!
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Fair enough, or likely to be way off? And what's the more accurate way of calculating it?