The mass per unit volume of paper/paperboard, indicating fiber compactness, typically expressed in g/cm³ or kg/m³.
Quick calc:
Density ≈ GSM ÷ (caliper in mm × 1000) → result in g/cm³.
Impact:
Higher density → generally stiffer, smoother, more opaque, but may increase crack risk at folds and overall weight.
Lower density → softer handfeel, bulkier/cushioning, but potentially lower strength and crush resistance.
How it’s tuned:
Calendering/pressing (wet or dry), fiber-to-filler ratios, and refining all adjust density.