No, that is not quite right... you need to use a factor to determine just the amount of OILS needed to build your soap formula for this size of cylinder mold. For a 3" wide tube that is 15 inches long you will do this: [(1.5 x 1.5) x 3.14] x 15 = 105.98 radius squared x pi x length of tube then do this final calculation to compensate for you only needing the OILS calculation, not the ENTIRE volume of finished soap: 105.98 x the factor of .38 = 40.27 oz of base oils the full math formula to determine the amount of oils for a cylinder is: [(1.5 x 1.5) x 3.14] x 15 = 105.98 x .38 = 40.27 radius squared x pi x length of tube factor oils needed Now calculate your lye and water. If you want a faster way, and have Excel on your computer, download the Chris Mathes SoapSheet3.1 .. it it at the TOP of my website as a download link: http://www.southernsoapers.com called SOAPSHEET3.1 Build your soap recipe normally, then CLICK ON THE AUTOSCALED tab at the bottom. That worksheet lets you toggled between Rectangular molds and CYLINDER MOLDS! And it does ALL the Math For YOU, grin! Here is a link to a screen shot of my using the Cylinder function for a soap formula: http://www.makeitsoap.com/images/math.h1.jpg Kelly Bloom Southern Soapers Fragrances ~ "We Have No Common Scents!" http://www.southernsoapers.com