Calculating target FG and my NB Choco Milk Stout

[eazaay]

Sooo I'm still a noob and have a question about calculating the estimated FG for a batch. I buy my extract kits from Northern Brewer but none of the recipes state a target FG. My first few batches have been real low FG (around 1.010) so I figured that was good enough. My last batch stopped at about 1.020 and now this is my second one slowing at 1.020. I'm not sure if that's normal or not So how can I calculate the FG when its not explicitly stated?

The kit I'm using this time is a Chocolate Milk Stout (recipe here) and it's been in the primary for 2 weeks now. I was going to move to secondary to add the cacao nibs but I thought 1.020 was too high. I was reading about FG and attenuation rates and the attenuation percentage is currently at ~57% but the yeast strain should eat up to 67-71%. The sample I tested was still a little fizzy too.

Here are my questions for this batch:

1) How can I kick start the yeast to eat up some of those leftover sugars?
2) Am I reading too much into attenuation rates for an extract brewer?
3) Is that 10% difference in attenuation a big deal?
4) The fizz is obviously CO2...are those calculators for adding priming sugar accurate for the amount of residual CO2 in each batch? (I'm asking because my last batch was a bit fizzy when bottling and I added the same amount of corn sugar as always but I had more head than beer when I poured it)

Thanks in advance for any and all info you can provide!!

 

[HH60gunner]

Does your kit give you a target ABV? If so you can take your OG and compare it with the 1.020 FG you got and see if it's close to the kits ABV. From what I've seen many kits usually have a higher FG than all grain, so this could possibly be what your FG is. Best test is to check your gravity to three consecutive days, and if it doesn't budge than it's safe to bottle. Also alot of stouts will normally have some unfermentables in them to give them that sweeter full body taste to them as well.

 

[user 19629]

The yeast should have an attenuation range.

 

[browndawg]

I brewed that kit and it finished up around 1.022. Generally sweeter stouts finish higher. That pound of lactose adds a couple of points as well.