How long is each length of each piece of the roll
https://www.bunnings.co.nz/mammoth-650mm-20m2-r1-5-underfloor-blanket-insulation_p0104424?srsltid=AfmBOopNDUt-cbArohvptCFGZFFd_JOmUft5PiM-pdcXb5WAwU9dDQn5
Covers 20 square metres. 650 mm wide.
Length therefore is 20 divided by 0.65 = 30 metres. (30.76m)
Hello @Mikedavis
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about insulation.
It's great that @Noyade has given you excellent advice in regard to the length of the insulation. He has given the spot on answer which is 30.76m.
If you have any other questions we can help with, please let us know.
Eric