# Topic: Re: How do you calculate the power required for helical impeller mixer?

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You left out one essential piece of information needed to calculate the power, and that is the rotational speed.&nbsp; So here are a the power requirements for a few appropriate speeds:&nbsp;&nbsp;&nbsp;&nbsp; 60 rpm&nbsp;&nbsp;&nbsp; 1,400 W&nbsp;&nbsp;&nbsp; 50 rpm&nbsp;&nbsp;&nbsp; 936 W&nbsp;&nbsp;&nbsp; 40 rpm&nbsp;&nbsp;&nbsp; 599 W&nbsp;&nbsp;&nbsp; 30 rpm&nbsp;&nbsp;&nbsp; 337 W&nbsp;The viscous power number for the impeller is 312.&nbsp; Viscous power number is Power divided by all the following (Viscosity times Rotational Speed squared times Impeller Diameter cubed).&nbsp; Of course the units of the variables must be consistent to obtain a dimensionless relationship.
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