Commercial & Compliance
Tonnage Measurement
Tonnage measurement is required for vessel registration, flagging and many commercial operations. SVG Marine measures and documents gross and net tonnage to international convention standards.
Tonnage measurement is the standardised calculation of a vessel's internal enclosed volume — not its weight. It is required by flag states for registration, and it underpins port dues, manning requirements and many commercial regulations.
SVG Marine attends the yacht as your independent yacht surveyor, takes the necessary measurements, calculates GT and NT in line with the International Tonnage Convention 1969 (or simplified UK measurement for smaller vessels), and prepares the formal tonnage certificate documentation for the registry or flag state.
Frequently asked questions
What is tonnage measurement?
Tonnage measurement is the calculation of a vessel's internal volume — expressed as Gross Tonnage (GT) and Net Tonnage (NT). It is not the boat's weight. Tonnage is required by flag states for vessel registration and underpins port dues, manning requirements and many commercial regulations.
When do I need a tonnage measurement?
Tonnage measurement is required when registering a yacht on Part 1 of the UK Register, when changing flag state, when bringing a vessel into commercial operation, and whenever a flag state or class society requests a formal tonnage certificate.
Who can carry out tonnage measurement in the UK?
Tonnage measurement for UK registry must be carried out by an MCA-authorised tonnage measurer. SVG Marine is an MCA Certifying Authority Examiner and undertakes measurement to either the International Tonnage Convention 1969 or the simplified UK measurement for smaller vessels.
How long does tonnage measurement take?
On-board measurement typically takes a few hours for a standard yacht. Documentation and certificate issue normally follow within one to two weeks.
Is tonnage the same as the yacht's weight?
No. Tonnage measurement is a calculation of internal enclosed volume, expressed in tons of 100 cubic feet (or cubic metres equivalent), and does not represent the displacement or weight of the vessel. Two yachts of the same physical weight can have very different gross and net tonnage figures.
Which tonnage standard applies to my yacht?
Vessels of 24m load-line length and above are measured under the International Tonnage Convention 1969 (ITC69). Smaller vessels can usually be measured under the simplified UK measurement rules, which are quicker and less expensive. SVG Marine confirms the applicable standard at quotation stage.
Do I need tonnage measurement for insurance?
Insurance is normally based on length, value and use rather than tonnage. However, tonnage is required for UK Part 1 registration, change of flag, commercial operation, port-dues calculation and many manning regulations — and many lenders require Part 1 registration, which in turn requires a tonnage certificate.
Can tonnage measurement be combined with another survey?
Yes. Tonnage measurement is regularly carried out alongside a pre-purchase yacht survey, an MCA coding examination or a new-build yacht inspection, which usually reduces total cost and attendance time.
Where do you carry out yacht tonnage measurement?
Throughout the UK — Southampton, the Solent, the South Coast and South Wales — and across the Mediterranean and wider Europe for UK and Red Ensign Group registered yachts.
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