1. What is Gross Registered Tonnage?

Definition: Gross tonnage (GT) is a unitless index related to a ship's total internal volume calculated from the total enclosed volume of the vessel.

Purpose: It's used to determine things like manning regulations, safety rules, and port fees, rather than representing actual weight.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( GT \) — Gross tonnage (unitless)
• \( K \) — Coefficient (typically 0.2–0.3)
• \( V \) — Total enclosed volume in cubic meters (m³)

Explanation: The coefficient accounts for the fact that not all enclosed space is usable. The formula was standardized by the IMO in 1969.

3. Importance of Gross Tonnage Calculation

Details: GT determines a ship's regulatory requirements, safety equipment needed, port dues, and is used for official registration.

4. Using the Calculator

Tips: Enter the coefficient (typically 0.25) and total enclosed volume in m³. The coefficient must be between 0.2 and 0.3.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between gross tonnage and deadweight tonnage?
A: Gross tonnage measures volume capacity while deadweight measures weight-carrying capacity (cargo, fuel, etc.).

Q2: Why is gross tonnage unitless?
A: It's an index number calculated from volume, not an actual measurement of weight or volume.

Q3: When would I use a coefficient other than 0.25?
A: Different ship types might use different coefficients - cruise ships often use higher values near 0.3, while cargo ships might use lower values.

Q4: How do I find the total enclosed volume?
A: This is normally calculated from the ship's plans by measuring all enclosed spaces below decks and in superstructures.

Q5: Is this the same as net tonnage?
A: No, net tonnage subtracts non-cargo spaces (engine room, crew quarters) and is typically about 30% less than gross tonnage.