Phosphorus is generally undesirable in steel. Decreasing availability of low phosphorus iron ores and the desire to recycle waste materials like basic oxygen steelmaking (BOS) slags is driving renewed interest in phosphorus removal. A number of phosphorus partition (LP) equations have been proposed in the literature for specific slag compositions and temperature ranges at equilibrium. These LP equations have been evaluated against the historic data on the phosphorus removal from an industrial top blown bottom stirred basic oxygen convertor. Further, the performance of these partition equations has been used to inform the development of a new LP model more suitable to the prevailing conditions in the Australian steelmaking industry. The new model has been used to isolate the key factors controlling dephosphorisation, namely lower temperature, higher basicity and higher oxygen potential. This LP model has allowed secondary factors influencing dephosphorisation to be assessed, including TiOx load, heat duration and stirring rate.