Calculation Question on OG

Hi all!

I am relatively new to home brewing (just did my 7th batch on Monday).
I had a quick question regarding gravity.

Each one of my brews I measured, had an incredibly high OG. Much higher than I anticipated or the BeerSmith calls for. Initially I thought I just hit the mother load, but I think I have discovered a flaw in my measurements.
I basically add the 3 gal of wort to the bucket after cooling and then top it off with 2 gal of water, with a good amount of aeration that occurs.
When I take my measurement though, I tap a sample from the spigot at the bottom of the bucket, which is probably not well mixed with the water, thereby giving the effect of a much higher reading.

My question is this: Is there still a way to guestimate/calculate a more accurate OG?

Any insight will be most appreciated!

Welcome to the board. To guestimate what the OGs that you already have, I would just use what Beersmith calculated. In my experience, it's OG calculations are fairly accurate.

In the future, it sounds like you know what to do. Just ensure proper mixture of your wort and top off water and you should get an accurate reading! Shake the **** out of it and take a sample! That's what worked for me