# how do you calculate sweetness?



## reefman (Jan 27, 2013)

Many wines I buy have a percentage of sugar on the label.
If I know my batch size and the lbs of sugar added, what's the calculation to get the percentage...it's escaping me at the moment.


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## novalou (Jan 27, 2013)

reefman said:


> Many wines I buy have a percentage of sugar on the label.
> If I know my batch size and the lbs of sugar added, what's the calculation to get the percentage...it's escaping me at the moment.



Each gallon of wine weighs approx 8.3 lbs. So that makes 42 lbs per 5 gallons.

If you add 1 lb of sugar to backsweeten, 1/42 x 100% = 2.38%


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## hobbyiswine (Jan 27, 2013)

Residual sugar is not a percent per volume but rather measured as grams per liter. For example if you have 75 grams of sugar in a 750ml bottle than you have 10% residual sugar. If you have 15 grams of sugar in a 750ml bottle than you have 2% residual sugar.

This is pretty easy to figure out if you are back sweetening a dry wine but a bit more tricky of you have a wine that has sugar left in it from stopping the ferment early, etc.

one cup of sugar has about 190 grams of sugar so I use that number when calculating RS of backsweetened wines.


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## novalou (Jan 27, 2013)

hobbyiswine said:


> Residual sugar is not a percent per volume but rather measured as grams per liter. For example if you have 75 grams of sugar in a 750ml bottle than you have 10% residual sugar. If you have 15 grams of sugar in a 750ml bottle than you have 2% residual sugar.
> 
> This is pretty easy to figure out if you are back sweetening a dry wine but a bit more tricky of you have a wine that has sugar left in it from stopping the ferment early, etc.
> 
> one cup of sugar has about 190 grams of sugar so I use that number when calculating RS of backsweetened wines.



Metric use this formula, US units, mine works the same.


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## reefman (Jan 29, 2013)

thanks, got it now. I was having one of those Senior moments.


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## Julie (Jan 29, 2013)

It make this more simple than doing the calculations, take a hydrometer reaidng of the commercial wine, now just bring your level up to that.


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## JetJockey (Mar 6, 2013)

*SG, ABV, & Residual Sugar?*

I wanted to calculate my Dragon Blood's ABV and Residual Sugar %.

I've seen a couple formulas using the initial SG and final SG to calculate the ABV. In my case, the Initial SG was 1.077 and the final (before back sweetening) was 0.991. The formulas use anywhere from 131 to 135 times the difference between initial and final SG. If I use 132 x (1.077-0.991) = 11.35% ABV.

I found the Quick Reference Guide to Estimating a Wines ABV and Residual Sugar in 3 Easy Steps. According to the very scientific research and calculations on website: http://www.rochesterwinemakers.org/...icles-by-members/guide-est-abv-and-res-sugar/ there is a direct correlation between the final SG and ABV to the residual sugar %.

Using Rochester Winemakers' 3-step method for my DB, the residual sugar/extract (various non-sugar compounds in wine like tannin, acids, glycerol, & pigments) is about 1.8%. Step 3 subtracted the extract component that has contributed to the final RS from the calculated combined extract/RS: 1.8% - 2.2% for white grapes/other fruit = DRY (-.04%). I guess you can't have drier than dry of 0% - maybe we should have a dry, extra dry, etc.!

With my Dragon Blood, I back sweetened my 6+ gallons (volume not known exactly) with 6 cups of sugar to get the SG after back-sweetening to 1.012. How do I account for the additional sugar being added to calculate the true residual sugar?

The Rochester Winemakers Website states "For accurate results, use an SG taken before sweetening as your final SG. Of course you’ll then have to update the residual sugar amount with the new sugar." I'm struggling with how to add my DRY or 0% residual sugar with the 6 cups of added sugar (back-sweetened) to get the final RS%. I don't have the weights of the 6+ gallons of pre-sweetened dry DB to take a % by weight of 6 cups of raw sugar @ 250 g = 1500 g / x grams of 6+ gallons of DB wine.

Any suggestions to calculate the RS?


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## Arne (Mar 6, 2013)

I just use sweetened to 1.010 or 1.005 or whatever makes it taste right to me and leave it at that. Arne.


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## saramc (Mar 6, 2013)

Good article http://www.winemakermag.com/stories...iques/501-measuring-residual-sugar-techniques

And if you happen to be in-the-know with a commercial shop almost all of them have the equipment to verify RS, so you may be able to get them to test your wine.

Another good article/method here http://www.rochesterwinemakers.org/...y-members/determining-abv-and-residual-sugar/


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