Typical values
Typical length-to-beam ratios ( aspect ratios) for small sailboats are from 2:1 (dinghies to trailerable sailboats around ) to 5:1 (racing sailboats over ). Large ships have widely varying beam ratios, some as large as 20:1. Rowing shells designed for flatwater racing may have length to beam ratios as high as 30:1, while a coracle has a ratio of almost 1:1 – it is nearly circular.Rule of thumb - formula
The beam of many monohull vessels can be calculated using the following formula: : Where LOA is Length OverAll and all lengths are in feet. Some examples: * For a standard yacht: the cube root of 27 is 3, 3 squared is 9 plus 1 = 10. The beam of many 27 ft monohulls is . * For a Volvo Open 70 yacht: 70.5 to the power of 2/3 = 17 plus 1 = 18. The beam is often around . * For a long ship: the cube root is 9, and 9 squared is 81, plus 1. The beam will usually be around , e.g. Seawaymax. As catamarans have more than one hull, there is a different beam calculation for this kind of vessel.BOC
BOC stands for Beam On Centerline. This term in typically used in conjunction with LOA (Length overall). The ratio of LOA/BOC is used to estimate the stability of multihull vessels. The lower the ratio the greater the boat's stability. The BOC for vessels is measured as follows: For a catamaran: the perpendicular distance from the centerline of one hull to the centerline of the other hull, measured at deck level. For a trimaran: the perpendicular distance between the centerline of the main hull and the centerline of either ama, measured at deck levelOther beams
Other meanings of 'beam' in the nautical context are: *Beam – a timber similar in use to a floor joist, which runs horizontally from one side of the hull to the other athwartships. *Carlin – similar to a beam, except running in a fore and aft direction. *Beam – the direction across the vessel, perpendicular to fore-and-aft; something lying in that direction is said to be ''abeam''.References
Notes
* * {{Ship measurements Nautical terminology Ship measurements