Diablo III Ancient Legendary drop rate

The 2.1.2 patch notes that introduced Ancient legendaries stated that they could only drop from Torment I and higher:

• Ancient items can now drop at Torment I or higher
  • The drop chance will increase with each Torment level

Based on the Diablo Wiki, the chances go from 1.5% for Torment I, up to 10% for T6.

The odds increase on higher levels of Torment, from around 1.5% on Torment 1 up to 10% on Torment 6 (from monster drops).

Note that this doesn't include Kadala or crafting; those chances are not known, but are probably a set rate to preclude doing so in T6 to maximize chances.