Stock Measurements

Degrees Plato (°P) is used to quantify the concentration of extract (mainly sugars derived from malt but also including other soluble material in wort) as a percentage by weight. A 10°P wort will contain 10 g of extract per 100 g of wort.

The measurement of wort gravity is important to brewers in that it is an indicator of the potential alcoholic strength of the beer.

 
As a very rough guide, every 1°P generates approximately 0.4% alcohol by volume

A 12°P wort will produce an average of approximately 5% alcohol by volume, depending on the extent to which sugars are fermented out.

 
The Plato scale differs slightly from the Balling scale in that the measurement of the specific gravity used to determine the dissolved solids content is carried out at 20°C for the Plato scale and 17.5°C for the Balling scale.

Brewers measure the degrees Plato using either a calibrated refractometer or a hydrometer. The Plato scale is used by most brewers worldwide, although brewers in the UK and those using British brewing traditions prefer to use the specific gravity scale instead.

This is derived by measuring the specific gravity of the wort (where water is 1.000), multiplying by 1,000, and then subtracting 1,000 from that figure to give the degrees of gravity.

Thus, a wort with a specific gravity of 1.048 is said to have 48 degrees of gravity.
 
The Plato and gravity scales can be approximated by multiplying the °P by 4 to give the degrees of gravity.
 
A 12°P wort is therefore approximately 48 degrees of gravity.