A common objection to the use of balancing tests in human rights adjudication is that it is not possible to perform a quantitative comparison between gains and losses for rights or the public good by means only of rational criteria. Here I provide a general account of the incommensurability objection, with the aim of making explicit its scope, and of dispelling some common misconceptions surrounding it. Relying on this account, I engage with recent defences of balancing against the incommensurability objection.