AleArchive | Calculators | Specific Gravity to Plato

SG to Plato

This calculator converts gravity reading between specific gravity (SG)
and degrees Plato (^{o}P).

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About this Calculator

What is Specific Gravity (SG)?

In brewing Specific gravity (SG) is simply the density ratio between
a sugar solution and pure water. For example, a sample with a specific gravity of 1.040
is 1.040 times more dense than pure water. As more sugars are dissolved the
solution, the density, and thus the SG, increases.

What is Degrees Plato (^{o}P)?

In brewing, degrees Plato (^{o}P) is the ratio of the weight of dissolved
sugar in a solution to the total weight of the solution. In other words,
^{o}P represents the percentage of a solution’s weight that is made up by the
sugar dissolved in the solution. A 10 ^{o}P solution would contain 10% sugars
by weight and the rest water.

Converting from SG to ^{o}P

The formula used for this calculation was taken from Page 312
in “New Brewing Lager Beer” by Gregory J. Noonan. The most precise
formula presented by Noonan is as follows:

To obtain the inverse relationship to convert from ^{o}P to SG, a
series of points were plotted in Microsoft Excel using the formula presented by Noonan
with ^{o}P as the independent variable and SG as the dependent variable.
A 3rd order polynomial was fitted to the data, and the resulting equation was obtained: