In 1992, the estimate of mature female green turtles associated with the French Frigate Shoals was set at roughly 750. The green sea turtle is the largest hard-shelled sea turtle. Adults of this species commonly reach 100 cm in carapace length and 150 kg in mass. The average size of a female nesting at the French Frigate Shoals was reported in 1980 to be 92 cm straight carapace length, with an average body mass of 115 kg. This is somewhat smaller than her Atlantic cousin .
Hatchlings are black on top and white underneath.
The plastron of the Hawaiian green turtle becomes orange or yellowish orange, and the carapace remains predominantly black with various shades of olive and yellowish gold forming swirls and irregular patterns on their shells. Growth rates of juveniles, sub-adults, and adult turtles measured by George Balazs at seven resident sites in the Hawaiian Archipelago revealed substantial variation. Along the Kau coast of the island of Hawaii, annual growth was approximately 4.50 cm to 6.25 cm. At the French Frigate Shoals, annual growth ranged from approximately .25 cm to 1.50 cm. These differences are probably a function of food availability and quality.