Enter the boat length (ft), the boat breadth (ft), and the boat depth (ft) into the Boat Gross Tonnage Calculator. The calculator will evaluate the Boat Gross Tonnage. 

Boat Gross Tonnage Formula

The following formula is used to calculate the Boat Gross Tonnage. 

BGT = .5*BL*BD*BW /100


  • BGT is the Boat Gross Tonnage (tonnage)
  • BL is the boat length (ft) 
  • BD is the boat breadth (ft) 
  • BW is the boat depth (ft) 

To calculate the boat gross tonnage, multiply the boat length, breadth, and depth together, divide by 2, then finally divide by 100.

How to Calculate Boat Gross Tonnage?

The following steps outline how to calculate the Boat Gross Tonnage.

  1. First, determine the boat length (ft).
  2. Next, determine the boat breadth (ft). 
  3. Next, determine the boat depth (ft). 
  4. Next, gather the formula from above = BGT = .5*BL*BD*BW /100.
  5. Finally, calculate the Boat Gross Tonnage.
  6. After inserting the variables and calculating the result, check your answer with the calculator above. 

Example Problem:

Use the following variables as an example problem to test your knowledge.

boat length (ft) = 40

boat breadth (ft) = 10

boat depth (ft) = 8

BGT = .5*BL*BD*BW /100 =  ?