[Acidicme]

If you have a 1.75%W/W of benzalkonium chloride
How much water would you need to make up a 1.33mg/ml concentration of 5L?

[Hunter2]

Basic mathematics.
Calculate how much you need if 1,75%  = 1,33 mg
This gives the value per ml. Then calculate up to 5 l. Normaly you need the specific gravity to convert 5 l in kg. The Difference from 5kg is the amount you have to add.