I have typically just gone off of how much I elect to put into my 401k each paycheck, which was 50% this past year. Technically, I was saving more than that, as I usually had some leftover cash that I would put into savings, so I often ballparked this as "a little over 50%".
Of course, this only lasts until the 401k is maxed out, after which I'm usually saving a commensurate amount, but it also gets weird because I have giving goals, which I don't consider to be "savings", and I occasionally do buy some more expensive items for myself. I should probably track that more closely. New job does not currently allow me access to a 401k but pays more than the last, so I think I can expect to be hitting 60% easily starting in January :)