Function to calculate display size as inches on android for Appcelerator Titanium with the help of https://github.com/dbankier/HasMenu

physical_size.js

/**
 * Calculates the physical display size for android devices
 * e.g 4,95 for Nexus 5 or 7,02 for Nexus 7
 * 
 * IMPORTANT: this requires https://github.com/dbankier/HasMenu
 * 
 * @return {Number} size as inches
 */
function getPhysicalSize(){
    // some infos we need
    var pfWidth = Ti.Platform.displayCaps.platformWidth,
        pfHeight = Ti.Platform.displayCaps.platformHeight,
        navigationBar = !require('yy.hasmenu').hasMenu,
        orientation = Ti.Gesture.orientation;
    
    
    // adapt value where appropriate 
    if (navigationBar){
        if (orientation == Ti.UI.LANDSCAPE_LEFT || orientation == Ti.UI.LANDSCAPE_RIGHT){
            // if in landscape, add navigation bar size to width
            pfWidth += 48 * Ti.Platform.displayCaps.logicalDensityFactor; 
        }else{
            // if in portrait, add navigation bar size to height
            pfHeight += 48 * Ti.Platform.displayCaps.logicalDensityFactor;
        }        
    }
    
    // calculate physical values
    var physicalWidth = pfWidth / Ti.Platform.displayCaps.xdpi;
    var physicalHeight = pfHeight / Ti.Platform.displayCaps.ydpi;
    
    // pythagoras stuff
    var inch = Math.sqrt(physicalWidth * physicalWidth + physicalHeight * physicalHeight);
    
    return inch;
}