View Full Version : Question about mead math and yeast....

11-17-2008, 04:03 PM
Ive just finished reading the 'The Compleat Meadmaker' by Ken Schramm , I have read through the Newbee Mead guide, I already have a list of 'must make' (the first of which will be JAO and the second a simple show mead kit to get some experience) Ive never brewed before, and I have questions before I start and get my self into trouble, if someone has a moment...

how do I calculate what the final SG should be, I suspect this has to do with my original gravity and the yeast used and its alcohol tolerance but I'm getting underpants gnome syndrome: step 1: take OG with hydrometer, step 3: perfect not exploding mead.

and related: how do I know how far a yeast will take the SG down?

How do I calculate the ABV? and the Brix? and do I even need to worry about those?

were do I find what SG a yeast can tolerate?

((I'm sorry if Ive some how missed this information. Ive searched the forums and don't seem to be finding what I think I need and Ive poked at the mead calculator, but either its not working for me or I'm not understanding the results.....))

11-17-2008, 05:18 PM
Hi BlueCrow,

I was "raised" on using Specific Gravity (SG) instead of Brix so I'll coach this in terms of Gravity Points. It all translates to Brix but I'll let someone who uses Brix (Pete?) chime in on it's use.

Gravity Points: It can easier to work with gravity points instead of specific gravity. Gravity points are derived by SG - 1 X 100. So an SG of 1.132 = 1.132 - 1 X 100 = 132 gravity points. In other words just drop the one and the decimal!

Approximating Final Gravity (FG): This is a feature missing in the Mead Calculator. I use ProMash to help me with this but here is a quick (and rough) rule of thumb. 1 gravity point will translate to approximately 0.133% abv. Example: an Original Gravity (OG) of 1.100 yields a Potential Alcohol By Volume (PABV) of ~13.3%. So if you have a must of 1.140, you have a PABV of ~18.6% (140 X 0.133 = 18.62).

Yeast Tolerance: Now, let's look at yeast. From the GotMead main site (not the forum) look under Mead Menu > Making Mead > Yeast Table. It will take you to this page (http://www.gotmead.com/index.php?option=com_content&task=view&id=625&Itemid=42). We can see that D47 has an alcohol tolerance of 14%. That means that it can eat approximately 14 / 0.133 = 105 gravity points. That leaves an estimated FG of 140 - 105 = 35 gravity points or 1.035, a sweet mead.

If you want a dry mead, adjust your OG or your yeast accordingly. In this instance the 1118 yeast has a tolerance of 18%. It would probably take this must all the way to dryness. Or, you could still use the D47 but shoot for a lower Original Gravity.

Alcohol By Volume (ABV): To determine the final ABV of your mead: OG points - FG points X 0.133 = ABV

Remember, these are just rough guidelines but the do get you in the ball park. Some people use brix more often than specific gravity but I was "raised" on gravity points so that's what I use. There are conversion charts out there to convert one way or the other but I don't have any links handy.

Your mileage may vary!


11-17-2008, 05:32 PM
Thank you Wildaho!

That was the math I was missing, or brain was not registering. :)

11-17-2008, 07:35 PM
Just a clarification:

You can use the Mead Calculator to determine how much honey to acheive a desire ABV/ABW

Step 0: Make sure the "Current Gravity" is set to SG=1.000 if you are starting with nothing but an empty carboy, or set it to the current SG of what is in your carboy.

Step 1: "Target Volume" - Tick the box and set the size of the final volume
(eg 5 gal if a 5 gal carboy)

Step 2: "Target Gravity: - tick the box and enter either the target SG/Brix/Baume or the target ABV/ABW into either of the two text boxes (entering an SG will display the associated ABV and vice versa)
and click the mouse somewhere on the page to cause the calculator to update all the boxes in the calculator.
(Eg, set the ABV to 18.0 )

There is a bit of a bug here, in that rounding errors change the 18 to something less. Just change the values in the SG/Brix/Baume field to get to the ABV/ABW figure you want

Step 3: The result you want (amount of honey to add) is displayed as the "Additional Sugars #1",
and you can change Type to be some other fruit or sugar or ...
and you can change the "Sugars Content" if you think your honey has a different water to sugar ratio.

Step 4: Remember, as you change values in in any of the fields on the calculator, click somewhere on a blank part of the calculator to trigger an update of all the fields.

11-17-2008, 07:56 PM
Damn, I knew that and forgot all about it!

It would still be nice to have a "Yeast Alcohol Tolerance" field to ease designing a semi to sweet mead at a specific ABV. The calculator is great for PABV but kind of chore to design for residual sugar. I do most of mine dry but the sweet mead questions pop up a lot here in the forums.


11-17-2008, 10:24 PM
just wanted to say thanks for this threat and your replies, I always forget where to find this info

11-18-2008, 12:22 PM
Thank you JamsesP, That calculator is awesome!

11-19-2008, 05:29 PM
Thanks, but do remember - it is limited.

The idea was to allow you to design your recipe to get you in the ball-park, but you have to use a hydrometer and adjust according to reality not theory 8)

or as the saying goes,
theory and practice are the same in theory, ... but not in practice.

11-19-2008, 05:49 PM
That's what I need, just enough to get me into real trouble in, and let me measure just how much trouble I'm in when I get there :)

I'm a ceramic artist outside of my 9-5 (famous any moment now....any moment...) and the thinking for make clay or glaze is really similar, which is part of what attracted me, also the mead. Mead is good.

But this will hopefully have fewer explosions.

11-19-2008, 07:05 PM
But this will hopefully have fewer explosions.

Don't bet on that! Search on "mead volcano" or "Mead Vesuvius" and you'll see what I mean! ;)