Might be a duplicate here: http://homebrew.stackexchange.com/questions/10823/how-to-calculate-alcohol-without-og-reading It appears that there is a formula using your Specific Gravity from a hydrometer and if you pick up a refractometer, a measurement from that, that you can use to calculate the ABV. Jump to section "Measurement of ABV" at [Brew Your Own](http://byo.com/stories/item/1313-refractometers) for the formula.