Calculation Methodology
The public formulas behind DIM penalty, billable weight, package fit, and packaging efficiency.
Last reviewed: August 31, 2026
Dimensional and billable weight
Dimensional weight is adjusted package volume divided by a rule-specific divisor, then rounded according to that rule. Billable weight is the greater of actual and dimensional weight. Thresholds and caps apply only when present in the verified rule version.
DIM Penalty
DIM Penalty = max(0, (billable weight − actual weight) ÷ actual weight × 100). A 5.2 lb package billed at 9 lb has a 73% penalty after rounding.
Packaging Efficiency Score
Formula version pack-eff-2026.08-v1 combines practical product-to-box fill (55 points), actual-to-billable weight efficiency (35 points), and a 10-point baseline. Fill credit reaches its maximum at 85% because some protective space is usually necessary.
- • 90–100: Excellent
- • 70–89: Good
- • 40–69: Needs Optimization
- • Below 40: Poor
Box optimization and fit
Single-item fit evaluates all six axis-aligned dimension permutations when rotation is allowed. Multi-item capacity uses an explicit grid approximation and is labeled approximate; it is not presented as exact 3D bin packing.
Versioning
Formula versions are immutable identifiers. Carrier rule changes create new records with new effective dates. Historical records are not overwritten.