pro rata
adjective
formal (also pro-rata) uk/ˌprəʊˈrɑːtə/ us/ˌproʊˈreɪtə/relating to a calculation of something such as pay or benefits according to a smaller number of hours worked, a smaller amount of something used, etc. in relation to the hours worked in a full time job, a larger amount of something used, etc.:
Part-timers should also get the same benefits as full-timers but on a pro-rata basis.
a pro rata refund/increase/share They may get a pro rata refund for the holiday they lost out on.
pro rata
adverb
She earns $40,000 a year pro rata.