Webster's Revised Unabridged Dictionary · 1913

Proportionable

Proportionable , adjective

Capable of being proportioned, or made proportional; also, proportional; proportionate.
But eloquence may exist without a proportionable degree of wisdom. — Burke
Proportionable, which is no longer much favored, was of our [i. e., English writers'] own coining. — Fitzed. Hall