Vessel Tonnage Calculator
Calculate GT, NT, and displacement for documentation
Tonnage Results
Gross Tonnage (GT)
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Net Tonnage (NT)
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Enclosed Volume
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Volume in Cubic Meters
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K1 Factor
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Documentation Required
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USCG Threshold
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Tonnage Thresholds (USCG)
| Gross Tonnage | Requirement |
|---|---|
| Under 5 GT | State registration only |
| 5+ GT | USCG documentation eligible |
| 25+ GT | Additional inspection requirements |
| 100+ GT | Licensed master required |
| 200+ GT | Full SOLAS compliance |
| 300+ GT | ISM Code compliance |
Understanding Tonnage
Types of Tonnage
Gross Tonnage (GT): Total enclosed volume of vessel - determines regulations that apply.
Net Tonnage (NT): Cargo/passenger carrying capacity - used for port fees.
Displacement: Actual weight of vessel - measured in long tons (2,240 lb).
USCG Simplified Method
For vessels under 79 feet: GT = 0.67 x L x B x D / 100
Net tonnage typically 80-90% of gross tonnage.
Official measurement requires USCG-approved measurer.