You can do it yourself...
Take the horizontal distance between the outboard ends of the boat not including rudders and bow sprits (iow, the centerline LOA). Multiply that by the maximum beam outside to outside. Multiply that by the distance from the sheer line not including bulwarks or cap rails to the outside bottom of the hull not including the keel. Add the volume of the deck house/cabin top. Multiply by .5 for sailboats and .67 for power boats. Divide by 100. This will give you the "Gross Tonnage". Net tonnage is 90% of gross for sailboats and 80% for power boats.
