Just finished fermenting my first attempt at making my own recipe, as a partial boil, but I have noticed something strange with my gravity readings.

Beersmith gave me a predicted OG of 1.051, but I had it in the fermentor at 1.059. The finishing gravity predicted at 1.013, and actual at 1.012, so far so good, with a predicted alcohol of 6.2%. Too high for the style, but so what?

The problem is this: As a sanity check, I tested the sample with a hydrometer and a refractometer (1.012 and 1.025 respectively). Putting these numbers in online calculators reveals ABV of about 4.2%, which is too low. This implies my starting gravity was about ~1.045.

These leads to two questions:

- Which alcohol measurement is correct; and

- If it's the second one, what did I do wrong in my initial measurements?

Any guidance would be appreciated in finding the flaws that lead to this situation.