Stock solution? 
A sodium thiosulfate stock soultion is a quanity of water and sodium thiosulfate of which we know that x amount will treat y amount of water containing z amount of chlorine. It is generally handy to make a stock solution which fits your normal water change needs. If I change 300 gallons of water ever week, then I would make a stock solution where 1 fl oz would treat the 300 gallons of replacement water at my given chlorine ppm. 
Calculator Usage: 
Enter the amount of stock solution you want, e.g., for 1 quart you would enter 32 fl oz.
Enter the amount of stock solution you wish to use at one time and the amount of water you wish to dechlorinate with that amout of the stock solution.
Enter the ppm of chlorine that needs to be dechlorinated.

Examples: 
You want 1 quart total and each 1 fl oz (30cc) should dechlorinate 1 ppm chlorine for 1000 gallons
Enter 32 fl oz in the Amount of stock solution field. In the Single Dose area, enter 1 fl oz and 1000 gallons. In the Chlorine ppm field enter 1.

Notes: 
Gallon = 128 floz
Quart = 32 floz
Pint = 16 floz
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