Genesis 16:16 - John Gill's Exposition of the Entire Bible

And Abram [was] eighty years old when Hagar bare Ishmael to Abram. Which is easily reckoned, for he was seventy five years of age when he left Haran, Genesis 12:4; and he had been ten years in Canaan when Hagar was given him by Sarai for his wife, Genesis 16:3; and so must be then eighty five years of age, and of course must be eighty six when Ishmael was born.