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Thought my last few beers were finishing way too high gravity. Wasn't sure if it was mash temp, cold ferment, inadequate aeration of wort...

Just noticed my hydrometer floating in a flask of starsan solution. Replaced the starsan with water to check. 1.004. What the fuck.

Guess I'm getting a new hydrometer.

Or just calibrate it! Use water and sugar in fixed amounts to see if it is just 4 points off everywhere. Then it is still easy to get a good reading.

BYO article about calibration

My hydrometer reads exactly the same; they must be twins separated at birth. One of these days I'll get around to doing a proper calibration, but for now I just assume it's reading 4 points to high everywhere on the scale. Good enough for me right now.

Did you account for temperature of the liquid? I believe hydrometers are generally calibrated in liquid at 15 or 20C.

Check online for a temperature adjustment calculator. The instructions that came with it will likely have a temp adj chart as well.

If it is still off, just do what the others recommend.

Mine is supposedly for 68f which is what I was measuring at.

I'll have to look up how to do the sugar water thing to see if it's equally off across the scale. I also was loaned a refractometer to see if I like that setup better.

For some reason I just assumed since the hydrometer is lead shot and glass that they would be made precise enough to not be this far off.

there are any number of reasons it could be off - eg, paper gradations slipped down a mm or two after adding shot, or a touch more glass got left at the top than normal when it was sealed. i only really use my hydrometer on a comparison basis - og to fg to calculate alcohol, and fg not changing to make sure ferm is done. otherwise, i judge a beer's sweetness by taste, not by bulk liquid density.