# Dry Matter Calculator

### Introduction

The Dry Matter Calculator determines the solids content of a wine from its alcohol content and specific gravity.  This is useful for winemakers who determine the alcohol content of their wines by other means, such as distillation or ebulliometry, and would like to calculate solids content.  Two methods are used to determine the solids content:

The calculator will adjust the hydrometer reading for temperature if the measurement temperature and the hydrometer calibration temperature are provided.  If the entered SG value is already corrected for temperature, or if temperature corrections are not desired, simply enter 20°C (68°F) in both of the temperature fields and no corrections will be made.  Details of the hydrometer temperature correction calculations can be found here.

This calculation is only valid for SG or density measurements obtained with a hydrometer or some other device for directly measuring SG or density.  It does not work with refractometer readings because of the obscuration effect of alcohol on refractive index.

### Input Field Definitions

Alcohol Content – The alcohol content of the wine.  Range: 0% to 100% vol/vol

Hydrometer SG Reading – The hydrometer SG reading for the wine sample.  Range: 0.77193 to 1.55454

SG Reading Temperature – The temperature of the wine sample at the time of the SG reading.  Range: 0°C (32°F) to 40°C (104°F)

Calibration Temperature – The hydrometer calibration temperature of the hydrometer used to take SG reading.   Range: 0°C (32°F) to 40°C (104°F)

### Output Field Definitions

Corrected SG (20°C/20°C) – The temperature-corrected SG value.

True Brix (Solids Content) – The total solids content of the wine calculated from alcohol content and the corrected SG value.

### Calculation Details

#### OIV Method

The OIV method is described in the Compendium of International Methods of Analysis by the The International Organisation of Vine and Wine (OIV, 2009).  This method assumes that solids (dry matter) cause the same increase in specific gravity in pure water as they do in wine.  The specific gravity of the alcohol-free wine is calculated as follows:

 sgr = sgv – sga + 1.0 (5-54)

where:

sgr = SG of the alcohol-free wine

sgv = SG of the wine

sga = SG of a water-alcohol mixture with the same alcohol content as the wine

The value of sga in equation (5-54) is calculated from the alcohol content using the OIML formula.  The solids content (true brix) is then calculated from the resulting value of sgr using the Brix conversion equation.

This method has a temperature basis of 20°C (68°F).

#### Hackbarth Method

This method utilizes the Hackbarth model, which allows calculation of SG given the alcohol and solids contents.  In this case, we must solve the equations iteratively for solids content given the SG and alcohol content.

This method has a temperature basis of 20°C (68°F).