Gravity reading. When/how for OG?

I've only done extract brewing until these last two batches, which were partials...

In the past, I boiled my wort, usually 2.5-3 gallons and took my O.G. reading from that, once cooled down.

Today I cooled the wort and didn't take my reading until after adding the extra water to bring the amount up to five gallons.

My reading came in at 1.041, the recipe says it should be 1.055.

I'm sure I could have gotten better efficiency from my grains.....

Did I take my reading correctly?

Welcome to brewing!

For extract batches take the gravity reading after diluting to 5 gallons and aerating so it is thoroughly mixed. If you take the reading before you dilute, that is the 'boil gravity' which is useful in calculating IBUs (hop bitterness, if you have gotten into the math on that yet).

Hydrometers are calibrated to 59F, that might have been a slight factor. The warmer the sample the lower the gravity reading.

Here is a calculator that helps adjust for that:
Hydrometer Temperature Adjustment Calculator | Brewer's Friend

When you add water it doesn't always mix evenly. Perhaps, with the water being thinner, it is sitting on top and only a bit of the sugars are mixing in. I would recommend stirring with a spoon or shaking it up before your next reading. Or... you could go with full boils .

ok, so I know I was warmer then 59. Not much though, my thermometer was around 64 or so. And I did pour the wort in the bucket, then water ontop of that without stiring. So my reading is probably off a tad from what it should be.

Good to know.
Thanks.

No need to worry about the final product though. The fermentation will mix everything easily. The only ill effect you will suffer is that your notes will not be as accurate as you may have liked. RDWHAHB. Cheers!