This app is a handy tool that can help you in calculating the petrol or diesel density of any given fuel. The user has to enter the temperature and the amount of fuel in the tank. The app will calculate the density of the fuel and display the value in both imperial and metric units. 

The user can also use the app to convert from one density to another. For instance, if you want to convert from liter to gallons per square inch, just enter the values in the boxes and click the 'Convert' button. 

The app is very useful for people who need to calculate the petrol or diesel density of any given fuel.