One concern that people will raise about converting to Kotlin is the number of methods added by its standard library. Thanks to massive libraries like the support library and GMS, many apps are in danger of bumping up against the Dex method limit. I used the dexcount gradle plugin to break down the method count before and after the rewrite. The end result is that the total method count after proguard decreased by 10% from 5491 to 4987 (not counting GMS or appcompat). The code count decreased by 30% from 12,371 lines of Java, to 8,564 lines of Kotlin.