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The filter paper method for measuring soil water potential was evaluated. The method was calibrated using salt solutions (-1.4 bars to -22.4 bars), sample chamber psychrometer (-1 to -50 bars), pressure plate (-0.1 to - 15 bars) and soil column at equilibrium (0 to -0.2 bars). It was found that the absolute temperature had little effect on the predicted soil water potential, but a temperature variation had a large effect. It was found that the temperature fluctuation must be small. The predicted water potential was influenced by the type of contact of the soil with the filter paper. It is suggested that one filter paper be placed beneath the soil (good contact for liquid or vapour flow) and one filter paper be placed above the soil not in physical contact (allowing vapour flow only). The equilibrium between the filter paper and soil mass was essential completed by the end of two days and certainly by the end of five days.