Beam

What is a yacht's beam?

The beam is the maximum width of a yacht's hull, measured at its widest point and expressed in metres or feet. It is one of four primary dimensions used to describe any vessel, alongside length overall (LOA), length at the waterline (LWL) and draft. Where LOA tells you how long the yacht is, the beam tells you how wide it is, and together with draft these dimensions determine whether a given yacht will physically fit a particular berth, lift, dry dock or canal.

Naval architects distinguish between several beam measurements. Beam overall is the maximum width including any protrusions such as rub rails or fender brackets. Beam at the waterline is the width where the hull meets the water at the design displacement, and is the figure that matters most for hydrostatic stability calculations. Moulded beam is measured to the inside of the hull plating and is used in structural drawings. For marketing and brokerage purposes, beam overall is the figure normally quoted in specifications.

Beam has a direct effect on the yacht's character. A wider beam provides more interior volume, particularly in the main saloon and master suite, and generally improves initial stability at rest. A narrower beam reduces wetted surface and wave-making resistance, which typically benefits efficiency at speed. Modern superyachts tend toward wider beams than older designs, driven by owner demand for interior volume and beach-club layouts, with typical beam-to-length ratios in the order of 1:5 to 1:6.

Why it matters for yacht owners

Beam dictates two things owners care about: how much usable interior the yacht offers, and where it can physically berth. Premium Mediterranean marinas such as Monaco's Port Hercules, Porto Cervo and Antibes Quai des Milliardaires impose width limits on their berths, and a yacht whose beam exceeds the limit simply cannot be accommodated regardless of length. Equally, a generous beam unlocks the full-width master suites, beach clubs and main saloons that define the modern superyacht interior. Owners specifying a new build should view beam as a deliberate trade-off between interior volume, berthing flexibility and seakeeping, not simply a number to maximise.

Key facts

• Beam is the maximum width of the hull, measured at the widest point and expressed in metres or feet.
• It is one of four primary dimensions, alongside LOA, LWL and draft.
• Beam overall includes any protrusions such as rub rails; beam at the waterline is used for stability calculations.
• A wider beam typically delivers more interior volume and better initial stability at rest.
• A narrower beam reduces wave-making resistance and typically improves efficiency at speed.
• Modern superyacht beam-to-length ratios are typically in the order of 1:5 to 1:6.
• Premium Mediterranean berths impose width limits - exceeding them rules a yacht out of those marinas entirely.
• Beam, together with draft, determines compatibility with lifts, dry docks and shipyard travel hoists.