Buy first: a hydrometer + test jar (Brewer's Elite combo class) for OG into the fermenter and FG before packaging. Add later: a Brix/SG refractometer (aichose-class) for mash runoff and pre-boil drops—then keep the hydrometer for FG, because alcohol skews raw refractometer readings.
Gravity readings tell you whether fermentation finished or just got shy. Fancy displays don’t help if you never calibrate. These tools sit next to the measurement basics in the starter kit guide.
Two jobs, two tools
Hydrometer + trial jar — Drop it in a tall sample, read specific gravity, correct for temperature if the wort isn’t at the hydrometer’s calibration temp (often 60°F / 68°F—check the scale). Cheap, trustworthy for original and final gravity. Glass breaks when you knock the jar against a kettle. Samples take more wort than a refractometer drop.
Refractometer (Brix / SG) — A few drops on the prism, fast mash runoff and pre-boil checks, less beer wasted. Before fermentation, it’s excellent once calibrated with distilled water. After alcohol shows up, raw readings lie; you need a correction formula or spreadsheet. Plenty of people “confirm” a stuck beer that wasn’t stuck—just misread.
ATC (automatic temperature compensation) claims still deserve a water calibration check. Trust, then verify.
A practical buying order
Most beginners should start with the hydrometer. You’ll use it for OG into the fermenter and FG before packaging, and you won’t need software to interpret the number. Add a refractometer when brew day speed and tiny samples start mattering—then keep the hydrometer for FG confirmation.
Sanitize the test jar and hydrometer like anything else that touches cooled wort (sanitizer guide). A dirty trial jar has infected more than one “mystery” batch.
After you can trust the numbers
Measurement won’t fix fusel heat—that’s temperature control. Faster brew days after the boil belong to a wort chiller. More in brewing guides.