Stupid Hydrometer - How much alcohol is there?

[TheBreweryUnderground]

So a few weeks ago I brewed up a monster RIS with an OG north of 1.15, at least I think I did. The problem is that my hydrometer has been acting up lately and I figured this out when a 1.1 IIPA had finished below 1. I think I've been getting much higher efficiency when I thought I wasn't, but I can't really tell because the hydrometer appears to have some condensation on the inside and can't tell me the gravity of water. So I had not yet gotten another hydrometer because I'm lazy and cheap so the OG is unknown. Is there anyway at home I can tell how much alcohol this stout has without the OG? It would be nice to know so that I don't accidentally get blackout drunk off of a glass, but that might just happen anyway. I'll pick up a new hydrometer and take a reading in the next day or two.

 

[helibrewer]

You could calculate the potential OG from your grain bill.

 

[TheBreweryUnderground]

I've done that, but the problem is this was such a monster beer I'm not sure if I got enough boil off or if the overnight mashing got a higher efficiency than expected. I'm guessing it is anywhere between 13% to 17%, but that's like drinking 3 beers or 4 beers worth of alcohol at a time. It'll definitely have to be a drink where I just stay at home afterward.

 

[beerkrump]

If you have access to a refractometer, you can figure out the OG if you know the FG from a hydrometer and the refractometer reading of the final beer.

The bottom equation here can do it.

 

[TheBreweryUnderground]

Thanks beekrump, I knew I had read about something like that at some point in time and that's exactly what I'm going for. Now I need to find a refractometer...