Here is the formula. It looks a little intimidating, but once you use it a few times it's like simple math.

A few things you should know right at the beginning. Like all formulas you have to know all the values except the unknown; the unknown being how much cure to add to the brine. For this formula, to find out how much cure to add, you need to know the weight of the brine (that includes the liquids, salt and sugar), the amount of sodium nitrite in the cure mix (when using cure #1, Prague Powder #1 - that amount will be 0.0625); and finally what ratio of sodium nitrite (ppm) you want the final brine to have.

Though this formula will calculate the amount of cure needed to bring the brine up the ppm you predetermined, it does not calculate the actual final ppm the meat has absorbed. This is due to the amount of salt in the brine – more salt means faster curing times. The temperature of your refrigerator – the colder the slower the curing times etc. Injecting can bring the ppm very close to the amount of ppm in the brine, but for smaller, thinner cuts of meat like duck breast, it is not necessary to inject. Just remember you are not making a commercial product that has to meet federal standards exactly. You are making a home product that is safe to consume. As I mentioned in an earlier post the safe ppm range for sodium nitrite in a wet brine to have a safe product is 40ppm - 200ppm. If you are planning to fry the cured food, you should keep you ppm around 130ppm - 156ppm. Though you will not probably be injecting, you need to keep that part into the formula, or I find the formula will not work.

Formula:

X = Amount of cure mix

Y = PPM (sodium nitrite parts per million that you determine you need)

W = Total weight of the brine.

N = Sodium Nitrite

Z = percentage of injection

X = Y x W/ Z x N x 1,000,000

Example: X is the unknown; and you want the sodium nitrite to be at 150 ppm. So now you have you first value of 150 ppm. The total weight of the brine; water (and most liquids, such as the coffee, maple syrup) will weight 8.33 pounds per gallon. So if you use a half gallon of liquid that will be 4.16 pound, plus the Diamond Cryptal Salt will be about .3 lbs. (5 oz.); that makes your brine approximately 4.46 lbs., we will plug in a percentage of 10%; that is your third value, the sodium nitrite is already known to be 0.0625. Though it will not be necessary to inject your duck breast, the formula won't work correctly if you don't plug in that value 10% makes it easier to calculate.

x = 150 ppm x 4.46 lbs. / .10 x 0.0625 x 1,000,000

x = 669 ppm-lbs. / 6,250

x = 0.10704 lbs.; rounded off to .11 lbs.

Since the amount of cure mixture is in pounds, unless you have a scale that reads pound to the hundredth; you must finish the formula by converting pounds to ounces.

So X = 1.76 oz.

It is early; so hopefully may math is correct.