Alcohol By Volume (ABV) From Gravity Calculator
The formula for calculating ABV (alcohol by volume) from a starting and final gravity reading is:
ABV = (initial gravity – final gravity) x 131.25
In this formula, the initial gravity is the specific gravity (density) of the unfermented wort or must, typically measured before fermentation begins using a hydrometer. The final gravity is the specific gravity of the fermented beverage, measured after fermentation is complete.
To use the formula, subtract the final gravity from the initial gravity and multiply the result by 131.25. The result will be the ABV of the fermented beverage. For example, if the initial gravity was 1.060 and the final gravity was 1.010, the calculation would be:
ABV = (1.060 – 1.010) x 131.25 = 6.5625%
Therefore, the ABV of the fermented beverage would be approximately 6.6%. Keep in mind that this formula is an estimation and may not be completely accurate, as it assumes that all of the sugar in the initial gravity reading is converted to alcohol during fermentation, which may not always be the case.
Allowing For Temperature Adjustment:
If temperature adjustment is needed when measuring the initial and final gravity readings, you can use a correction factor to account for the difference in temperature.
The formula for temperature correction is:
Corrected gravity = (measured gravity – 1) x ((1.00130346 – 0.000134722124 * temperature + 0.00000204052596 * temperature^2 – 0.00000000232820948 * temperature^3) / (1.00130346 – 0.000134722124 * reference temperature + 0.00000204052596 * reference temperature^2 – 0.00000000232820948 * reference temperature^3)) + 1
In this formula, the measured gravity is the actual gravity reading, and the temperature is the temperature at which the reading was taken. The reference temperature is the temperature at which the gravity reading would be accurate, typically 20°C or 68°F.
To correct the gravity reading for temperature, you would first use this formula to calculate the corrected gravity for both the initial and final gravity readings, using the same reference temperature for both. Then, you can use the corrected gravity readings in the ABV formula mentioned in my previous answer.
Keep in mind that precise temperature control is important when measuring gravity readings, as even small temperature differences can affect the accuracy of the readings and the calculation of ABV.
|Temperature (°C)||Temperature (°F)||Correction Factor|
To use this table, you would measure the specific gravity of the wort or must at the actual temperature using a hydrometer. Then, find the correction factor in the table for the corresponding temperature and add or subtract it from the measured specific gravity to get the corrected specific gravity at the reference temperature of 20°C or 68°F.