OG measurement

In the last brew I did a yest starter (OG=1035 1 liter)
In Beersmith 2 I have specified a "Starter size" of 1 liter and I have put a checkmark into "Add Starter to bottling volume"
Now my 2 questions are:
1) When should I measure OG. Is it before I add the yeast starter to the fermenter- or is it after ?
2) Is "Measured batch size" with or without the yeast starter volume (1 liter in my case) ?

Thanks in advance

For me, I measure the OG before I add my yeast starter.  However, I crash out the yeast in the fridge and decant most of the liquid on top. I'm not sure how to handle the OG reading with a large starter added, since some of the starter wort will have been converted to alcohol by the yeast.

The batch size is the amount of wort produced that you will pour into your fermentor.  When you click to add the yeast starter, it adds this to the bottling volume and not your batch size.  So if you are making a 20 liter batch and adding a 1 liter starter, you will need 21 liters of space in your fermentor.

Thank you for the answer. I fully agree with you that logically OG should be measured before adding the yeast starter for the reasons you mention. Also adding the yeast starter to the bottling volume in Beersmith makes good sense, but I still think something is missing.
Shouldn't Beersmith compensate OG for 1 liter yeast starter with OG=1035 mixed up with 21 liter wort in the fermenter with OG=1092. I think of a formula like this:
OG measured value= 1092 (21 liter wort) + OG=1035 (1 liter Yeaststarter) =  1000+(92*20/21 +35*1/21)=1089,3
This means 0,4 % alcohol in difference (assuming Measured FG=1019)

In my latest receipe I have "downgraded" measured OG from 1092 to 1089 by using this calculation method. This makes a relativ high deviation from "Estimated ABV" and ofcoarse it also influences on the breweing efficiency

I dont know if this makes any sense

Regards from Lars

Lars, you're thinking of the decanted starter as if it's all wort. It's mostly yeast and won't have an appreciable effect on your gravity. The gravity contribution of remaining wort is 20% or less of the total volume.

The technique that Oginme outlined and the reasoning behind it are spot on. In BeerSmith, the brewing efficiency is derived from your recipe. The ingredients in your starter are not calculated, since by definition, starter wort is a separate recipe.

When you're looking at adding enough liquid volume to appreciably change the alcohol content, then your final starter phase should be close or the same as the recipe gravity. This particular method is Krausening, where partially fermented beer is married to another batch. It can be applied to new wort, or used later for fermentation cleanup and carbonation.

Thank you for the very fine explanations to both of you
I think I understand now why trying to calculate the OG impact from the starter doesn't make much sense. I guess the reasonable thing to do is to get rid of most of the water from the starter.
/Lars