proportional
adjective
°At a constant ratio (to). Two magnitudes (numbers) are said to be proportional if the second varies in a direct relation arithmetically to the first.
"The stopping distance is proportional to the square of the speed of the vehicle. — at physicsclassroom.com."
°In proportion (to), proportionate. More common in US than UK.
"...how much of the Bush administration's immediate post-9/11 emphasis on Iraq was appropriate and proportional to the overall picture of terrorism — '''' retrieved 24 Jan 2005."