Gravity Reading Help

Recently brewed a beer that missed OG by 0.002. While I doubt this is noticeable, at what point would the beer's taste change? At what point would you think about taking action? 0.005? 0.01?

what kind of brew? extract or AG?

Off hand I'd say that if it is extract, you either have just a bit more water in it, or it wasn't mixed well. It is very hard to get the wrong og with extract.

Worrying about the OG at the 3rd decimal point isn't practical, most of our volume measurements have too much error. Also, the fermentability of extract varies quite a bit so it is going to vary.

If you are plus or minus .005 no worries. If it's off more than that just adjust with water or extract. It very hard to get a good OG reading if doing partial boils due to the incomplete mixing of high gravity wort and plain water. If you are doing full boils, your OG readings should be pretty accurate, just remember to correct for temperature.

This is for all grain

I have brewed a honey kolsch numerous times within .005 of my first attempt. Not having done a side by side, I haven't noticed any difference. On that, a pale ale I've brewed I missed by .01 and that was tragic(got a little messed up drinking some Pliny before the brew day. Won't make that mistake again).

.005 gravity is 25 points of sugar on 5 gallons. Which sounds like a lot (about 1lb of 2row with typical conversion if I recall the references right, or about 1/2 lb of DME).

I'm guessing you won't notice a flavor or body difference. IF you are really concerned, get 1/2 lb of pale/light DME and add it in. But I'd personally not worry about it, unless you are making a beer that was 'light' ie target ABV of like <3% Then it might be important.

also a .005 gravity could be the difference of an extra bit of water, about 1/2 gallon I think (I've not worked the math)