Paper Strength Calculator

A heavier sheet is inherently stronger just because it has more fiber packed into each square meter, so comparing raw tensile, tear, or burst numbers across grades of different weight is misleading. Dividing each raw result by grammage produces tensile index (N·m/g), tear index (mN·m²/g), and burst index (kPa·m²/g) — figures that let you compare fiber quality and furnish independent of how heavy the sheet is.

Breaking length is the theoretical length, in kilometers, of a hanging strip of the paper that would snap under its own weight — the calculator gets it by dividing the tensile index by 9.81 (converting the force-per-grammage relationship into a gravitational breaking point). It's a classic normalized strength benchmark in papermaking that lets mills compare grades without worrying about sample width or exact test geometry.

Tensile Energy Absorption (TEA) is computed from both tensile force and stretch-at-break percentage together (0.5 × tensile × stretch fraction), so it captures the toughness of the whole stress-strain curve rather than just the peak force. A stiff, high-tensile sheet that breaks at very low elongation absorbs less total energy than a somewhat weaker sheet that stretches further before failing, which is why TEA and tensile index can rank grades differently.

The fold endurance figure comes from an empirical log-log formula (log(folds) ≈ 1.5×log(tensile index) + 2.0×log(stretch%) − 1.0) rather than a physical folding test, so treat it as a coarse indicator of whether a grade sits in poor, fair, good, or excellent territory. Because fold behavior is also sensitive to fiber furnish, test direction, and conditioning humidity that this model doesn't include, an actual MIT double-fold tester result can diverge meaningfully from the estimate.