Enter Enclosed Space Volumes
Use the responsive input grid below. Large screens show three columns, medium screens show two, and mobile screens show one.
Example Data Table
This example shows how individual enclosed spaces combine into the total volume used by the calculator.
| Space Category | Example Volume (m³) | Comment |
|---|---|---|
| Hull Enclosed Volume | 5,400 | Main enclosed hull structure |
| Superstructure Volume | 1,150 | Bridge and upper enclosed sections |
| Engine Room Volume | 680 | Machinery enclosure |
| Cargo Space Volume | 2,950 | Hold or internal cargo compartment |
| Accommodation Volume | 420 | Crew and service accommodation |
| Tank and Service Volume | 310 | Service tanks and enclosed utility spaces |
| Miscellaneous Enclosed Space | 90 | Other enclosed areas |
| Workshop | 75 | Optional custom enclosed space |
| Total Enclosed Volume | 11,075 | Illustrative total volume |
| Illustrative K1 | 0.280887 | Calculated from log10(11,075) |
| Illustrative Gross Tonnage | 3,110.82 | Official rounded-down figure: 3,110 |
Formula Used
Gross tonnage is estimated from the total volume of all enclosed spaces. The calculator first sums each entered enclosed space volume to obtain V.
K1 = 0.2 + 0.02 × log10(V)
GT = K1 × V
Official displayed GT = floor(GT)
Where V is total enclosed volume in cubic metres, K1 is the tonnage coefficient, and GT is gross tonnage. The raw result is shown together with the official rounded-down value.
How to Use This Calculator
- Enter the vessel name and optional project reference for your report.
- Input each enclosed space volume in cubic metres.
- Use the custom field for any extra enclosed compartment.
- Choose the display precision you want for shown decimals.
- Press Calculate Gross Tonnage to display results above the form.
- Review the total enclosed volume, K1 factor, raw GT, and official rounded-down GT.
- Use the chart to compare the contribution of each entered space.
- Download the report as CSV or PDF for records, planning, or review.
FAQs
1) What does gross tonnage measure?
Gross tonnage measures the vessel’s total enclosed internal volume through a standardized tonnage formula. It is not the ship’s weight, cargo mass, or displacement.
2) What volumes should I include?
Include all enclosed spaces you want counted in the gross tonnage estimate, such as hull spaces, superstructure, machinery rooms, cargo spaces, accommodation, tanks, and other enclosed compartments.
3) Why is an official rounded-down result shown?
Many tonnage certificates present the final gross tonnage as a whole number without decimals. Showing the rounded-down value makes the result easier to compare with formal reporting practice.
4) Is gross tonnage the same as displacement?
No. Displacement relates to the mass of water displaced by the vessel. Gross tonnage is derived from enclosed volume and serves regulatory, administrative, and comparative purposes.
5) Why does the K1 factor change with volume?
K1 depends on the base-10 logarithm of total enclosed volume. As vessel volume increases, K1 increases gradually, which changes the gross tonnage result in a controlled way.
6) Can I use this for preliminary design studies?
Yes. It works well for early estimates, internal checks, tender studies, and comparison exercises. Formal certification should still rely on approved tonnage measurement and official review.
7) What happens if a custom space is left blank?
If the custom volume is zero or empty, the calculator simply ignores that line. If volume is entered without a name, the tool labels it as a custom enclosed space.
8) Do export files include the chart and summary?
The CSV export includes the numerical summary and detailed breakdown rows. The PDF export includes the summary and attempts to include the Plotly chart image on a second page.