Block Coefficient
Abbreviation: Cb
Ratio of underwater volume to a rectangular block of length × beam × draft.
In practice
Vessel particulars list Cb. The OOW uses it indirectly via the loading instrument's hydrostatics. High Cb (>0.85, VLCC) means sluggish manoeuvring; thrust-to-weight ratio is low.
Regulatory detail & full definition
The block coefficient (Cb) is the ratio of a ship's underwater volume to that of a rectangular block of length by beam by draft: Cb = V / (L · B · T). It is a quick measure of hull fullness: VLCCs and bulk carriers run a full Cb of about 0.85, container ships about 0.65, ferries about 0.5, and yachts and naval vessels lower still. Naval architects use it in resistance-estimation methods such as Holtrop-Mennen and Guldhammer-Harvald and as shorthand for the trade-off between cargo capacity and speed.
Related
Source: Standard naval architecture; IMO MSC/Circ.1184 (resistance)
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