A closed form hydraulics equation was derived in this study to predict bottomhole pressure during drilling in inclined boreholes. The analytical model was developed on the basis of bubbly flow. It considers the effects of injected liquid, injected gas, formation fluid influx, and drill cuttings on bottomhole pressure. Different friction factor correlations are used for aerated liquids with and without foaming agents. The equation was tested with data from two field-drilling cases involving a shallow (212 m vertical depth) horizontal well drilled with aerated mud and a vertical well drilled with stable foam from 860 m to 884 m. The differences between the measured and equation-calculated bottomhole pressures are less than 2% in both cases. This work provides drilling engineers with an easy-to-use tool for designing aerated fluid drilling hydraulics.