Table of Contents
QBrew aims to be a simple streamlined homebrewing recipe calculator. As such, it doesn't include features that other software designed for professional brewing might include. This is not a flaw on the part of QBrew, but a conscious choice to moderate the scope of the software. Emails and forum posts praising the QBrew interface tell me that his was a good decision.
The basic gravity calculation is the sum of all grains' extract times quantity, divided by the batch size. Mashed grains will have their extract modified by the mash efficiency. Steeped grains will use a lesser efficiency, typically half of their extract.
The color calculated is in SRM, not in HCU (homebrew color units). HCU is the sum of all grains' color times quantity, divided by the batch size. This is only accurate for very low color values. The default conversion to SRM uses the formula discovered by Ray Daniels, which is SRM=(MCUx0.2)+8.4 (for values of HCU over 8.0). An alternate color calculation discovered by Dan Morey is SRM=1.4922x[(MCU)^0.6859] (for values of SRM less than 50). To change to the Morey method, open up the Configure... dialog and check the Use Morey color calculation box. More information on color calculations can be found at "Approximating SRM Beer Color" <http://hbd.org/babble/Color.htm>, and "Beer's Law" <http://www.brewingtechniques.com/brewingtechniques/beerslaw/morey.html>.
Final gravity is assumed to be 25% of the OG. Looking through the AHB style guide, this is the same assumption they made. The alcoholic content calculations were derived from Noonan's New Brewing Lager Beer, and based on this FG assumption.