# Topic: Re: How do I calculate the power required by a motor?

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This question has missing information about the impeller, which has been estimated to do the calculations.&nbsp; In addition to tank diameter and straight side, impeller dimensions are needed, like impeller diameter, blade width, number of helical ribbons, impeller height, and pitch of helix.&nbsp; Estimated values are impeller diameter of 92 inches, blade width of 9.2 inches, 2 helical ribbons, impeller height 138 inches, and helix pitch of 92 inches.&nbsp;I have never seen fluid viscosity in deci Pascal seconds, but that looks like 65 Pa.s, or 65,000 m Pa.s, or 65,000 cp.&nbsp; With those assumptions the impeller will draw about 620 hp, and a 750 hp motor recommended with a 220 mm diameter shaft.&nbsp; If the viscosity is really 650 m Pa.s or 650 cp, then the impeller power is112 hp, which could be handled with a 125 hp motor and a 127 mm diameter shaft.&nbsp; If the impeller is shorter, not as high, the power would be less, even for a 3,600 gallon batch, since impeller power is proportional to the submerged impeller height.
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