Why would we be interested in "lasts"?

There are lists of Dutch ships for the period 1628-1633 (and later) that only have "last" figures. If we want to put together fleets for gaming the Battle of the Downs, in 1639, we would want to know the ship sizes. The lists have a mix of detail, but they include crew and armament data for many ships. To use those ships in games, we would want to estimate their size, given the lasts figures. That is especially important because to calculate the English tonnage figure, we need to have estimates of the Dutch dimensions, first. The English burden is calculated as follows:

Burden in tons = (Length of the keel x Beam x Beam/2)/94. This gives you a gross tonnage. Privateers Bounty and other game systems generally base their ship capabilities on this figure.

A good approximation for converting Dutch measurements to English is:

English Keel Length = Dutch length from stem to stern / 1.33

English beam outside of planking = Dutch beam inside of planking / 1.13.

English depth in hold = Dutch hold / 1.13

This is approximate, but it is a starting point. Individual ships varied, but this is a good average. I have used the information from Dr. Weber's book on the Four Days Battle for Dutch ships taken by the English as the basis for these conversion factors. For many ships, he has the English and the Dutch measurements. Frank Fox helped him correct the English dimensions to fix copyist mistakes.