I think I asked the question too quick. Im not 100 percent sure how the numbers in a fertilizer are calculated, but if this is true, 20-0-0 would have 20 parts per million Nitrogen after it is mixed per instructions; then this would be true.
80G or just under 5 TBL spoons of KNO3 into one gallon of water would give you a 25-0-16 fertilizer, nitrogen-phosphate-potassium.

Here is a link that might be useful: Calculator

The 3 main numbers on a fertilizer package show the % by weight of Nitrogen, Phosphorus, and Potassium.

Al

Well done Al. The rest are inert ingredients.
Vernon

Here is what I found out. I have found that some fertalizers use NO3(nitrate) as nitrogen since nitrogen by itself is a gas and plants can not absorb this form of nitrogen.
So with that, KNO3 is pure fertilizer, I would have a 61-0-39 fertilizer. If you want to go buy pure nitrogen and have the oxygen as an inert ingredient then you would have a 48-0-38 fertilizer. I figured this out by going with the molecular weight percentage formula. amuE/amuT+amuE2/amuT+amuE3/amuT=100%

That does not answer the question, how much of KNO3 do I mix with a gallon of water for safe use on plants. Im guessing two-four tablespoons with a gallon.

correction, the 48-0-38 should read 14-0-39