For me, getting a refractometer was one of those upgrades that made a lot of difference.  With a refractometer you need a sample size of two drops.  I figured that this would pay for itself in beer savings alone.  I also had just broken my hydrometer and came to the realization that hydrometers are made of breakable glass that can break! 🙂

With the aid of calculators – get a Free Non-Expiring Brewfather Trial Account –  Refractometers can be used to measure gravity throughout the brewing process.