Estimate original gravity after the fact?

My first batch is about 8 days old now, and it seems like it's moving along very well. I'm going to keep it in my main fermentor for another 6-13 days before bottling. My last gravity reading from a few days ago was around 1.015

... the only problem is that I missed one totally critical step: my original gravity reading of the wort before pitching!

Additionally, my original recipe called for 3 x Briess Golden Light (3.3lb) LME, and I forgot to use the 3rd.

So i'm expecting my brew to be a lower ABV (total bummer) but I'd like to get some sense of what it might be?

Is there a way to take my ingredients and create what my (flawed) OG should be?

 

I did some searching around and found this:

Dry malt extract (DME) produces about 44 degrees per pound per gallon of water and liquid malt extract produces about 35 °.


To determine how much malt extract to use to reach a predetermined starting gravity, use this simple formula: (degrees of extract) x pounds of malt used by gallons of beer to be brewed. For example, if we use 6 pounds of liquid malt extract to make 5 gallons of beer, we would have 35 x 6 = 210... so, 210 divided by 5 (gallons of beer to be brewed) = 42, or a starting gravity of 1.042.

So for you I guess it'd be 35 x 6.6 = 231 / 5? = 46.2

Gravity = 1.046

That's assuming you made 5 gallons of wort and didn't add any other fermentables. Also, I'm fairly certain the "degrees" of different types of LME will vary, but I couldn't find the specific data for Briess Golden Light (3.3lb) LME, though I'm sure someone else might know.

Also, if I'm completely wrong (which is possible), please someone let us know.

EDIT: Okay, I did find that the default PPG (degrees) for Briess Golden Light LME is in fact 34. So the estimated OG would be 1.044, or rounded up to 1.045 (because the equation gave us 44.88).

 

Plug your numbers into a brew program. That should give you est og.

 

Would you recommend one for the iPhone or Mac?

 

Wow, great information! I really appreciate it. I'll try to plug my numbers into your formula. There was actually a bit more to my recipe, I steeped some grains, added some 1lb of dry extract and a few specialty malts as well.

 

Right on. Yeah, just look for the PPG of each of the grains and extracts you used and you should have a good idea of your starting OG. Cheers!

 

Any decent software should do the same. If it doesn't people will point it out.