A correlation is presented for predicting heat transfer coefficients during saturated boiling prior to critical heat flux in mini/micro channels in horizontal and vertical upwards flow. It is verified with data that include channels of various shapes (round, rectangle, triangle), fully or partially heated, horizontal and vertical upward flow, 17 fluids (water, natural and halocarbon refrigerants, organics, cryogens), diameters 0.38 to 3.0 mm, reduced pressure 0.0046 to 0.692, and mass flux 28 to 1500 kg m^-2s^-1. The new correlation predicts the 2412 data points from 64 data sets from 37 sources with a mean absolute deviation of 19.9 %. Several other correlations were also compared with the same database; all had significantly higher deviations. The correlation has also been validated with data for macro channels.