# Correction formula for alcoholmeter

I need to find the formula, if there is one, which would calculate the correction of alcoholmeter.

Basically convert observed %ABV (Alcohol by volume) to actual %ABV using the sample's temperature.

I know the correction tables, but I am looking for the formula or do I have to use tables?.

• No doubt there is a formula. Not knowing what you are measuring or what table you are using, I can't find the formula for you. – MaxW Feb 5 '17 at 19:17
• So this is a table I am talking about homedistiller.org/correctiontable.pdf They even have online calculator for it homedistiller.org/calcs/husker_temp_convert.php – MrAzgra Feb 5 '17 at 19:54
• I'm too lazy to dig for this. The technique uses a hydrometer which is probably calibrated to read %ABV at 20 C. So you need to find an equation for the density of an ethanol-water mixture as a function of ethanol concentration and temperature. – MaxW Feb 5 '17 at 22:57
• starting at web2.airmail.net/sgross/fermcalc/fermcalc_alcohol.html you should be able to find what you need... – MaxW Feb 5 '17 at 23:17
• @MaxW, probably shouldn't have even brought up the polynomial thing. That said, the problem I've seen is that with modern spreadsheets it's too easy for anyone to calculate up to a 9th order polynomial and say ~"look, I've fitted it with r^2 =0.9999" ! – airhuff Feb 5 '17 at 23:18

## 1 Answer

I have had the same question recently. And there is no simple answer. Tables (like ones from International critical tables of numerical data, physics, chemistry and technology or this) are still the 1st hand source. Formulas used are just approximating this data. Check formula here on page 8 (to get the temperature-corrected ABV you have to invert it by solving non-linear function). Alternatively check this recent study. To convert between ABV (alcohol by volume, %) and density (specific gravity SG, g/cm3) you may use this approximation:

$$\mathrm{SG} = -0.002\cdot\mathrm{ABV} + 1.0012$$

PS. There is an unconfirmed formula at vinolab:

The hydrometer temperature correction for SG is performed with this expression:

$$\text{corrected-reading} = r \times \frac{(1.00130346 - (0.000134722124 \cdot t) + (0.00000204052596 \cdot t^2)\ - (0.00000000232820948 \cdot t^3))} {(1.00130346 - (0.000134722124 \cdot c) + (0.00000204052596 \cdot c^2)\ - (0.00000000232820948 \cdot c^3))}$$

where: $$r$$ = reading and $$c$$ = calibration temperature. This expression is based on °F, so the temperatures are first converted.

With some sample values it gave me results close to the table' ones (I have converted ABV to SG, amended as per temperature and formula above and finally converted back to ABV).

• I think it wouldn't hurt if you include the formulas/data from each report you are referring to. URLs tend to rot over time. Also, the last formula taken from the report written by a student leaving John Doe from the template on the front page doesn't look convincing. Also, a tip: you can add #page=<number> (e.g. #page=8 ) at the end of the PDF's URL so that others open the document on that very page. – andselisk Feb 10 '19 at 0:00
• Formulas there are quite complex for my markdown skill. I have checked John Doe's formula against this data. It gives 0.8% discrepancy at worst. – Anton Krouglov Feb 10 '19 at 0:34