Warping & Sizing
Stretch taken in sizing is elongation the yarn no longer has at the loom. Keep it under 1.5%.
— %
Creel to beam elongation
The wet zone is where damage happens: yarn is weakest leaving the size box. Take any unavoidable stretch in the dry zones instead.
Stretch Percentage in Sizing Calculator — free, with the formula and a worked example, at Textile School.