can you work out alc vol without a starting reading

[tojo82]

Hi all I didnt take a reading of a vimto no added sugar concentrate hooch but wondered is it still possible to work out alcohol without a starting reading? It was 1 gallon with 490g sugar and ended at 0.996?

 

[Chippy_Tea]

If you tell me how much sugar there is total and what you are making it in i might be able to get somewhere near.