Drywall is typically 500 lbs/yd3. A 8 yd3 load is about 1.4 to 2.88 tons (typical 2.0 tons). Drywall is typically mixed debris, but moisture can materially widen weight risk. Range-based planning is safer than visual estimates.
Drywall is usually a weight-first decision surface. Treat volume as secondary after tonnage limits.