Osmolality can be converted into osmotic pressure based on the following equation:
Osmotic pressure = 19,300 x Osmolality (in mm of Hg)
Reference:
Zhang, M. and L. Song. (2000). Mechanisms and Parameters Affecting Flux Decline in Cross-Flow Microfiltration and Ultrafiltration of Colloids. Environmental Science & Technology 34(17): 3767-3773.