Power numbers in a baffled stirring tank with paddle-type impellers were measured over a range of Reynolds numbers, from laminar-to turbulent-flow regions. The impellers studied included a two-blade flat-paddle impeller, a 45 degrees two-blade pitched-paddle impeller, a 45 degrees four-blade pitched-blade turbine, and a two-stage pitchedblade turbine. The impeller-diameter-to-tank-diameter ratio was 0.5 to 0.6. The measured power numbers were compared with those derived from two other methods: prediction by using correlations and computational fluid dynamics (CFD). Power number correlations showed that the values estimated from the empirical correlations proposed by Nagata agreed closely with those measured in the laminar-flow region but deviated significantly in the transitional-and turbulent-flow regions. The power numbers derived from the correlation proposed by Kamei and Hiraoka agreed well with the experimental results in the laminar-and turbulent-flow regions. The power number in a stirring tank was also simulated by the CFD method. The numerical results showed satisfactory agreement with the experimental data over a wide range of Reynolds numbers.