Sugar to add..... Fact:  .125 pounds of sugar will raise 1 gallon 
1 brix or degree.  The rates below are subject to rounding off to the nearest tenth.    
Pounds of Sugar to Add per Gallon
to Achieve Desired degrees Brix
Starting
Desired Brix
Brix
21
21.5
22
22.5
23
23.5
24
10.0
1.4
1.4
1.5
1.6
1.6
1.7
1.8
10.5
1.3
1.4
1.4
1.5
1.6
1.6
1.7
11.0
1.3
1.3
1.4
1.4
1.5
1.6
1.6
11.5
1.2
1.3
1.3
1.4
1.4
1.5
1.6
12.0
1.1
1.2
1.3
1.3
1.4
1.4
1.5
12.5
1.1
1.1
1.2
1.3
1.3
1.4
1.4
13.0
1.0
1.1
1.1
1.2
1.3
1.3
1.4
13.5
0.9
1.0
1.1
1.1
1.2
1.3
1.3
14.0
0.9
0.9
1.0
1.1
1.1
1.2
1.3
14.5
0.8
0.9
0.9
1.0
1.1
1.1
1.2
15.0
0.8
0.8
0.9
0.9
1.0
1.1
1.1
15.5
0.7
0.8
0.8
0.9
0.9
1.0
1.1
16.0
0.6
0.7
0.8
0.8
0.9
0.9
1.0
16.5
0.6
0.6
0.7
0.8
0.8
0.9
0.9
17.0
0.5
0.6
0.6
0.7
0.8
0.8
0.9
17.5
0.4
0.5
0.6
0.6
0.7
0.8
0.8
18.0
0.4
0.4
0.5
0.6
0.6
0.7
0.8
18.5
0.3
0.4
0.4
0.5
0.6
0.6
0.7
19.0
0.3
0.3
0.4
0.4
0.5
0.6
0.6
19.5
0.2
0.3
0.3
0.4
0.4
0.5
0.6
20.0
0.1
0.2
0.3
0.3
0.4
0.4
0.5
20.5
0.1
0.1
0.2
0.3
0.3
0.4
0.4
21.0
0.0
0.1
0.1
0.2
0.3
0.3
0.4
21.5
0.0
0.1
0.1
0.2
0.3
0.3
22.0
0.0
0.1
0.1
0.2
0.3
22.5
0.0
0.1
0.1
0.2
The rates given above in the chart are subject to rounding off to the nearest tenth. The rates above are for pounds to add to 1 gallon.
Fact:   .125 pounds of sugar will raise 1 gallon 1 brix or degree.   
One ounce is .0625 pounds.  
One pound of corn (dextrose) sugar is 3 cups and
approximately 1 pound of table (sucrose) sugar is 2 ¼ cups.   
To calculate sugar using straight math:
 
To adjust the sugar to 210 or 220 brix.  We use corn sugar (dextrose), as it is a simple sugar ready for yeast consumption. Take the initial Brix reading. Compute the increase in brix desired (i.e. 15 to 21=60).  Estimate your gallonage after fermentation based on 12-13 pounds of fruit per gallon.  Approximate yield from 65 pounds of grapes (fermented on the skins) will be ~5 gallons. Multiply the increase of brix desired (6) by the number of gallons to be adjusted (5x6 gal=30).  As .125 pounds of sugar raises 1 gallon 10 brix, multiply this (30) by .125. That number will equal the pounds of sugar to add to the entire batch of must  (or crushed grapes) or juice.   The amount of sugar to add for this batch (30 X .125) is 3.75 pounds. Add the required sugar.  If you use cane sugar it is recommended to heat it in some of the juice.  The heat and acid will convert it to a simple sugar. 

Winemakers Depot - Your Trusted Source for Wine Making Information