Refracto is a user friendly tool for homebrewers that will help you to convert your refractometer measurements during a fermentation process from °Brix to SG or °Plato. It automatically compensates the alcohol effect during fermentation.

System Requirements: iPhone or iPad with iOS 10.0 or newer and a Refractometer with Brix scale.

How to Use Refracto

  1. Swipe vertically to enter your initial refracotometer reading, i.e. the measurement result for the original wort, just before adding the yeast.

  2. Swipe vertically to enter your current refractometer reading, i.e. a measurement result after the fermentation process has started.

  3. Swipe horizontally to switch between the computation modes. Available modes are the Standard formula, the Kleier formula and Sean Terrill’s linear and cubic formula. For general purpose usage the Standard and Kleier formulas compute the best results.

  4. You are done! In the upper part of the screen you can now see the computed values for your beer. The next section describes the computed values in detail.

How to use Refracto: Description of input areas.

Computed Values

Refracto computes the following values whenever you change one of its input values:

  1. The resulting Original Gravity (OG).

  2. The estimated alcohol concentration as percent by volume (ABV).

  3. The Final Gravity (FG), displayed on the top as apparent gravity and as actual gravity on the bottom. The apparent gravity corresponds to the value you would measure with a hydrometer. The actual gravity is a corrected value that compensates the effects of alcohol influencing a hydrometer.

  4. The amount of sugars consumed by the yeast so far, displayed as apparent attenuation on the top and as real attenuation below. In practice only the apparent attenuation is relevant.

The computed values can be customized. This is described in the next section.

Computed values: Detailed description of output area.


The settings tab allows you to configure Refracto to your needs. The available options are:

  1. Use this switch to select between a splendid bright and a stylish dark interface theme. The Screenshots section below shows both variants in full detail.

  2. The gravity unit to display computed values can be set to Plato (°P) or Specific Gravity (SG). Plato is traditionally used in parts of Europe, while the modern Specific Gravity is widespread in the US and UK.

  3. The Wort Correction Factor is used to convert your initial Brix reading of the unfermented wort into the Original Gravity. The brewing literature mentions typical values for this factor in the range from 1/1.02 to 1/1.06. By default Refracto uses a value of 1/1.03. If in doubt, set the Wort Correction Factor to 1/1.03 or 1/1.04 which are the most commonly used values.

Settings: Description of App options.

"After using this app, I'm going to put my hydrometer on a dusty shelf."

User “52guitars"

"Excellent companion."

User “Forquare"


Bright Interface

Bright Interface - Refractometer Tab - Configured for Plato
Bright Interface - Refractometer Tab - Configured for Specific Gravity (SG)
Bright Interface - Settings Tab

Dark Interface

Dark Interface - Refractometer Tab - Configured for Plato
Dark Interface - Refractometer Tab - Configured for Specific Gravity (SG)
Dark Interface - Settings Tab

Refracto is Open Source. Get the source code on