Bedforms commonly exist in fluvial channels and are vital in predicting flow resistance, sediment transport, and deposition within many rivers. The length and height of bedforms generated by lower regime flows and upper regime flows, respectively, are analyzed in this paper. Based on large number of flume and field data, it is found that flows and sediment parameters play different roles in bedform development in lower and upper regime. In terms of the bedform height, the gradation of sediment mixture plays an important role in the formation of bedform; the sediment size and gradation as well as the dimensionless grain radius in upper regime flows play negative roles, while the relative Shield parameter plays positive roles. For the bedform length, the sediment size plays a positive role in lower regime flows, and a negative role in the upper regime flows; the sediment gradation plays a negative role in lower regime flows, and a positive role in the upper regime flows; the dimensionless grain radius plays positive roles, but the relative Shield parameter plays negative roles. New formulae are proposed to calculate bedform height and length, which gives better predictions than other four representative methods.