Throughout the greater part of the eighteenth century, the ships of the East India Company, although large for their day, were very small when compared with contemporary ships-of-war. There had been some very large Indiamen in the late seventeenth century. Sixteen of them, built during the period 1675–80, had measured anything up to 1300 tons and could mount as many as sixty guns. But after the amalgamation of the Old and New Companies, the ships became smaller. This change was mainly due to naval jealousy with regard to the supply of large timber. As a result of the change the Indiamen of the early eighteenth century measured from 350 to 400 tons. They tended to increase slightly in size as the years went on, so that ships of 480 and 490 tons burthen became common; and from about 1735 onwards the latter tonnage became the most usual.

After 1750 an era of standardisation dawned in which all Indiamen were registered at 499 tons. This was more in the nature of a convenient fiction than a mathematical fact. It was somehow connected in men's minds with a law then in force by which vessels of 500 tons' burthen and upwards were compelled to carry a chaplain. Most of the ships had, in fact, a real tonnage greater than that assigned them on paper. They were all, nevertheless, of approximately the same size. So they remained until about 1773, when Indiamen of 676, 700 and even 800 tons began to multiply.