Forgot to take an OG reading...any hopes at reverse-calculating?

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thebigtruth

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I brewed a beer last night, and in the haste of trying to finish up and get everything cleaned before it got too late I forgot to take an OG reading. However, I did take gravity readings of first runnings from the mash and last runnings (stupidly not the mixed wort pre-boil). I had hoped to throw a hydrometer in the fermenter early this afternoon, but by the time I had a chance the yeast starter I added was already ripping away.

I've already come to terms with using my estimated gravity (I hit mash temps/times so I'm assuming efficiency to be close to estimated), but I was wondering if there was a way to calculate OG based off first running gravity and last running gravity?

Recipe

9# 2-Row
1# Dextrine
8oz Flaked Wheat
8oz Torrified Wheat

Mash Temp: 150F
Mash Time: 75 min

First Running Grav: 1.078
Last Running Grav: 1.017

Pre-boil Vol: 6.5gal
Post-Boil Vol: 5.5gal

Estimated OG: 1.057
Actual OG: ???
 

Desert_Sky

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Know your process and your equipment. You shouldnt fluctuate much if any from batch to batch.

Besides, even if you took a reading and its a bit off, whats it going to do beside make you worry at this point? No worries my friend, Its going to taste great
 

Mothman

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If you have a refractometer and hydrometer you can back calculate using a fg tool like https://www.brewersfriend.com/refractometer-calculator/

Use the fg calculator and enter your refractometer FG reading, the edit the OG reading until the resulting FG hydrometer reading matches what your FG hydrometer reading actually is... The OG it took to get the matching fg should then be close to what your og really was.

I think.

Lol
 

robbeh

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I wouldn't worry about it. 75% efficiency is really good in my eyes and you will hit your number within a small margin. I messed up a whole batch by fly sparging in a setup that is not ideal and missed my target by 12 points. Beer still turned out pretty good, just less ABV.

The important reading is the consistent FG to know she's done. I guess if you batch priming, go off the recipe target as I am sure you would have been close.
 

RM-MN

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Unless you need to calculate the brewhouse efficiency or the ABV, forgetting to take the OG is of no real consequence. If you think you aren't getting close to the OG you can just make a guess and add some DME but in most cases the beer will taste about the same.
 

Veets

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If you have a refractometer and hydrometer you can back calculate using a fg tool like https://www.brewersfriend.com/refractometer-calculator/

Use the fg calculator and enter your refractometer FG reading, the edit the OG reading until the resulting FG hydrometer reading matches what your FG hydrometer reading actually is... The OG it took to get the matching fg should then be close to what your og really was.
This
 

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