# Temp Correction Formula for Hydrometer

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#### jcarson83

##### Well-Known Member
Does anyone have a temperature correction formula for hydrometer. I found this one but its not working when I check against the tables I've found.

=1.313454-0.132674*t+2.057793*2.71828-3*t*2-2.627634*2.71828-6*t*3

This one works but is only accurate from 59 to 167F

=-2.52-0.0252*t+0.00112*t^2

The one I posted first is supposed to be accurate way above that.

I was begining to think that this thread needed to go into an "Advanced Techniques" section of the forum.

/I think I finally beat HB99 with the smart a\$\$ comment.

Thanks but I'm trying to put it in a spreadsheet so I need the equation. But it doesn't matter because my hydrometer only goes down to .99 which means I can only test wort at about 120F anyway. Though the correction isn't that big so I guess I could get pretty close at 170F.

There is a formula in Papazian's book, but I'm not sure where my copy is right now. If I find it I will post it.

jcarson83 said:
Does anyone have a temperature correction formula for hydrometer. I found this one but its not working when I check against the tables I've found.

=1.313454-0.132674*t+2.057793*2.71828-3*t*2-2.627634*2.71828-6*t*3

Maybe you just typed the wrong thing, but that should be:

=1.313454-0.132674*t+2.057793*2.71828-3*t^2-2.627634*2.71828-6*t^3

where ^ means "to the power of"

Other than that, I really have no idea what the above means. What is t? Do you add the above result to what you actually read? I don't get it...

t is Temperature. Yes you add the result to your reading. As the wort increases in temp it becomes less dense so unless it is cooler than 59F the result will be a positive number. The longer equation is supposed to allow you to correct results at higher temperatures.

Okay. I guess it's fairly useless to me without converting, as we use Celcius here in Oz!

I have a maths degree, and I find something a bit strange about the two formulae. Are you sure that the 't' you use isn't measured from some temperature other than zero in one or both of the formulae?

The reason I ask is that it doesn't make sense to have completely different numbers in a formula that is supposed to be accurate to higher temps. The first few terms should be the same; it should just have some higher-order terms (terms proportional to t^4, t^5 etc.)

In fact, looking back at your original formula, it seems really strange as written. Perhaps try typing it out again? For example
-2.627634*2.71828-6*t^3 to me means:

-(2.627634*2.71828) - (6*t^3)

That seems weird. Why aren't all the constant terms just incorporated together?

Brewsmith said:
I was begining to think that this thread needed to go into an "Advanced Techniques" section of the forum.

/I think I finally beat HB99 with the smart a\$\$ comment.
Ya got me there BS! Too much math in this post to get interested...I just add +1 or +2 and I'm done. Can't see all the fuss about large formula's when it's not necessary.

My chemistry is simple too! H2O is water and K9P comes from a dog.

Electronics? A Transistor is a nun who had a sex change...

Keep It Simple Smarta\$\$!!

You have the wrong formula. Here is the correct one:

C = ((1.313454 - (0.132674*F) + (0.00205779 * F^2) - (0.000002627634 * F^2)))

Where F = Temperature in degrees Fahrenheit.

C = Correction

So,

CG = C + (SG * 0.001)

Where,

CG = Specific Gravity corrected for temperature

C = Correction from above forumla

SG = Specific Gravity before temperature correction.

Here it is for everone using Degrees Centigrade:

C = ((1.313454 - (0.132674 * ((C * 1.8) + 32)) + (0.00205779 * (((C * 1.8) + 32))^2)) - (0.111112627634 * (((C * 1.8) + 32))^3)))

Then continue with the formula above formula for CG

If you would like to use Excel for this, do the following:

Degrees F calculation

1) Use Cell B3 as your temperature (F) input.
2) Use Cell B5 as your SG input
3) Paste the following into Cell B7:

=1.313454 - (0.132674*B3) +( 0.002057793*(B3^2)) - (0.000002627634*(B3^3))

Paste the following into Cell B9:

=B5+(B7*0.001)

Cell B9 will contain your temperature corrected SG

For people using degrees centigrade, change the formula pasted into Cell B7 to the following:

=1.313454-(0.132674*((B3*1.8)+32))+(0.002057793*(((B3*1.8)+32)^2))-(0.000002627634*(((B3*1.8)+32)^3))

I'm sure that I could have reduced the formula down to something "prettier", but I really didn't feel like wasting time doing that. Besides, isn't that what's so nice about using Excel.

Cheers!

Disclaimer = It is possible that I made a transposition error when transferring this from Excel, so please check the Excel results against a table before using it.

Damn thanks man I was looking forever for this formula for my excel sheet. Thanks dude

i believe the original formula was supposed to be

Correction = 1.313454 - 0.132674*T + 2.057793e-3*T^2 - 2.627634e-6*T^3

but this assumes a hydrometer that is calibrated to 59F. if your hydrometer is calibrated to a different temp like 68F then i don't think this formula will not work. I've been looking for a formula that can be used for any calibration temp but so far haven't had much luck.

i believe the original formula was supposed to be

Correction = 1.313454 - 0.132674*T + 2.057793e-3*T^2 - 2.627634e-6*T^3

but this assumes a hydrometer that is calibrated to 59F. if your hydrometer is calibrated to a different temp like 68F then i don't think this formula will not work. I've been looking for a formula that can be used for any calibration temp but so far haven't had much luck.

This is exactly the problem I am running in to. I am trying to create a set of calculators for mobile devices, phones and such. I have a few already working but can not seem to find the formula for the hydrometer that can be adjusted to different calibrations temps.

If there is any body out there better at math than I am they might be able to modify the above formula to include the calibration temp variable.

Thanks for the formulae. However, there is a problem!

Old fashioned hydrometers are calaborated at 15°C, but modern ones are collaborated at 20°C. The equation given before is for 15°C hydrometers. What makes it worse is that nowhere on line says which the string of numbers mean, or where they come from, so I can't develop my own 20°C equation.

I found a formula that will do hydrometer corrections no matter what your hydrometer is calibrated for. Mine, which is about 20 year old, is pegged to 70 degrees instead of the more standard 59 degrees.

This is the formula for Microsoft Excel:
Code:
``=A1*((1.00130346-0.000134722124*A2+0.00000204052596*A2^2-0.00000000232820948*A2^3)/(1.00130346-0.000134722124*A3+0.00000204052596*A3^2-0.00000000232820948*A3^3))``

Easily, the longest formula I've EVER typed into a spreadsheet. At least it works. I've tested the results against hydrometer correction charts in "How to Brew", "Brewing Quality Beers", and "Brewing Lager Beer".

There are some assumptions you will need to know for that formula to make any sense. Do this:
1) Create a new spreadsheet.
2) Cell A1 will hold your measured Specific Gravity reading. Type in 1.050 for testing purposes.
3) Cell A2 will hold your measured temperature. Type in 120 (I'm assuming Fahrenheit) for testing purposes.
4) Cell A3 will hold your hydrometer's calibration temperature. Mine is 70, but you can type in 59 since that's probably what yours is.
5) Copy and paste the above formula into cell A4.

If you used the values, 1.050 (measured s.g.), 120 (measured temp), and 59 (calibration), then you should see 1.0610 for your calibrated specific gravity reading.

I'm building a spreadsheet to help me plan my beers and I'm willing to give it away for free if anyone can tell me how to post it to this Forum.

Cheers,
Guido

I am thinking of building an open source home brewing and wine making calculator. What do you think?

Here Check this out. Link

That Beer Recipator link is awesome thanks

Thanks for the formula! I'm adopting various homebrew equations into my TI-86 graphing calculator so I don't always have to be by a computer.

Code:
``````Function sgRatio(Temp As Double) As Double
sgRatio = 1.00130346 - 0.000134722124 * Temp + 0.00000204052596 * Temp ^ 2 - 2.32820948E-09 * Temp ^ 3
End Function

Function corSG(SG As Double, Temp As Double, CalT As Double) As Double
corSG = SG * (sgRatio(Temp) / sgRatio(CalT))
End Function``````

I found a formula that will do hydrometer corrections no matter what your hydrometer is calibrated for. Mine, which is about 20 year old, is pegged to 70 degrees instead of the more standard 59 degrees.

This is the formula for Microsoft Excel:
Code:
``=A1*((1.00130346-0.000134722124*A2+0.00000204052596*A2^2-0.00000000232820948*A2^3)/(1.00130346-0.000134722124*A3+0.00000204052596*A3^2-0.00000000232820948*A3^3))``

Easily, the longest formula I've EVER typed into a spreadsheet. At least it works. I've tested the results against hydrometer correction charts in "How to Brew", "Brewing Quality Beers", and "Brewing Lager Beer".

There are some assumptions you will need to know for that formula to make any sense. Do this:
1) Create a new spreadsheet.
2) Cell A1 will hold your measured Specific Gravity reading. Type in 1.050 for testing purposes.
3) Cell A2 will hold your measured temperature. Type in 120 (I'm assuming Fahrenheit) for testing purposes.
4) Cell A3 will hold your hydrometer's calibration temperature. Mine is 70, but you can type in 59 since that's probably what yours is.
5) Copy and paste the above formula into cell A4.

If you used the values, 1.050 (measured s.g.), 120 (measured temp), and 59 (calibration), then you should see 1.0610 for your calibrated specific gravity reading.

I'm building a spreadsheet to help me plan my beers and I'm willing to give it away for free if anyone can tell me how to post it to this Forum.

Cheers,
Guido

Thanks for the formula Guido. Here is the same formula adjusted for temperate in Celsius:
Code:
``=A2*((1.00130346-0.000134722124*((B2* 9/5)+32)+0.00000204052596*((B2* 9/5)+32)^2-0.00000000232820948*((B2* 9/5)+32)^3)/(1.00130346-0.000134722124*((C2* 9/5)+32)+0.00000204052596*((C2* 9/5)+32)^2-0.00000000232820948*((C2* 9/5)+32)^3))``

Hey guys thanks for putting me on the right path but after punching all this data into a spreadsheet it seems to work with 5 and 10 degrees over (celcius... come on America we believe you can catch up lol) but 5 and 10 under it doesnt change the reading at all (which it should) im happy to give it out freely and let anyone alter it as long as they let me have a copy of the updated version, unfortunately i have nothing old enough to produce an xml spread sheet so i have converted it to an xls (close as i can get) and thrown it on the net for anyone with the link which is Brewing details.xml feel free to use it anyone

That seems weird. Why aren't all the constant terms just incorporated together?

2.71828 is the mathematical constant e.

I guess they aren't combined for clarity.

EDIT: Ignore this, I didn't see there was more than one page... oops!

I found a formula that will do hydrometer corrections no matter what your hydrometer is calibrated for. Mine, which is about 20 year old, is pegged to 70 degrees instead of the more standard 59 degrees.

This is the formula for Microsoft Excel:
Code:
``=A1*((1.00130346-0.000134722124*A2+0.00000204052596*A2^2-0.00000000232820948*A2^3)/(1.00130346-0.000134722124*A3+0.00000204052596*A3^2-0.00000000232820948*A3^3))``

Easily, the longest formula I've EVER typed into a spreadsheet. At least it works. I've tested the results against hydrometer correction charts in "How to Brew", "Brewing Quality Beers", and "Brewing Lager Beer".

There are some assumptions you will need to know for that formula to make any sense. Do this:
1) Create a new spreadsheet.
2) Cell A1 will hold your measured Specific Gravity reading. Type in 1.050 for testing purposes.
3) Cell A2 will hold your measured temperature. Type in 120 (I'm assuming Fahrenheit) for testing purposes.
4) Cell A3 will hold your hydrometer's calibration temperature. Mine is 70, but you can type in 59 since that's probably what yours is.
5) Copy and paste the above formula into cell A4.

If you used the values, 1.050 (measured s.g.), 120 (measured temp), and 59 (calibration), then you should see 1.0610 for your calibrated specific gravity reading.

I'm building a spreadsheet to help me plan my beers and I'm willing to give it away for free if anyone can tell me how to post it to this Forum.

Cheers,
Guido

Thank you so much for this. I didn't even consider that the exponents were getting formatted out when I was translating this formula. This was driving me nuts!

Here is a thought that might make your life a bit easier. About two years ago I bought calibrated hydrometers from a scientific supply house that measure in degrees Plato (the numbers are smaller and easier to work with, plus I was a pro brewer for about 6 years and we measured in degrees Plato). To get SG from degrees Plato, there are conversion algorythm in programs like BeerSmith that will convert the numbers if you want to stay in SG. (It is not a direct multiply by 4 conversion to get to SG). I have three; one from 0-8, one from 8-16, and one from 16-25. They were about \$20 apiece.

These hydrometers are laboratory grade and have an internal thermometer that give a correction factor of plus of minus tenth of degrees Plato. I just put the hydrometer in the beer, measure the gravity, and add or subtract the correction factor. I have measured beers accurately at up to 90 degrees F. Quick and easy, no math calculations necessary, I like quick and easy! I know that some online homebrew supply houses have SG hydrometers that have a correction thermometer in them that does the same thing, but they are not very accurate, from my experience. The ones I have are calibrated to an accuracy of less than 0.1 degrees Plato.

I know this is an old
I found a formula that will do hydrometer corrections no matter what your hydrometer is calibrated for. Mine, which is about 20 year old, is pegged to 70 degrees instead of the more standard 59 degrees.

This is the formula for Microsoft Excel:
Code:
``=A1*((1.00130346-0.000134722124*A2+0.00000204052596*A2^2-0.00000000232820948*A2^3)/(1.00130346-0.000134722124*A3+0.00000204052596*A3^2-0.00000000232820948*A3^3))``

Easily, the longest formula I've EVER typed into a spreadsheet. At least it works. I've tested the results against hydrometer correction charts in "How to Brew", "Brewing Quality Beers", and "Brewing Lager Beer".

There are some assumptions you will need to know for that formula to make any sense. Do this:
1) Create a new spreadsheet.
2) Cell A1 will hold your measured Specific Gravity reading. Type in 1.050 for testing purposes.
3) Cell A2 will hold your measured temperature. Type in 120 (I'm assuming Fahrenheit) for testing purposes.
4) Cell A3 will hold your hydrometer's calibration temperature. Mine is 70, but you can type in 59 since that's probably what yours is.
5) Copy and paste the above formula into cell A4.

If you used the values, 1.050 (measured s.g.), 120 (measured temp), and 59 (calibration), then you should see 1.0610 for your calibrated specific gravity reading.

I'm building a spreadsheet to help me plan my beers and I'm willing to give it away for free if anyone can tell me how to post it to this Forum.

Cheers,
Guido
I know this is old, but does anyone have the source/publication for this formula?

I know this is an old

I know this is old, but does anyone have the source/publication for this formula?
I know this isn't what you ask, but in 10°F of change from the calibration temperature, you are only going to be off by 0.001. Most of us really can't read our hydrometers within 0.002 on a good day.

Are you certain your hydrometer isn't calibrated for 20°C (68°F). That is usually what many hydrometers intended from the get go as beer hydrometers are calibrated for.
(never mind, I realize now I was reading what you quoted)

You could just take the SG of water at different temperatures and find out for yourself what your actual corrections should be.

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