Understanding the mechanisms of coral calcification is limited by the isolation of the calcifying environment. The boron systematics (B / Ca and δ11B) of aragonite have recently been developed as a proxy for the carbonate chemistry of the calcifying fluid, but a variety of approaches have been utilized. We assess the available experimental B / Ca partitioning data and present a computer code for deriving calcifying fluid carbonate chemistry from the boron systematics of coral skeletons.