Usually a reasonable estimate for most yeasts and recipes: Gravity points divided by 4. That's specific gravity but ignoring the 1.0 in front.

So, for 1.093, that's 93 / 4 = 23 which is 1.023.

However Denny is correct, the real number is very dependent on yeast strain and recipe, so if we have that, including mash times and temperatures, then we can refine the estimate further.

P.S. Another very rough guideline: If the OG is 1.093, then you should end up with roughly 9.3% ABV, plus or minus a few tenths. This works for many yeasts and recipes, but again... it depends.