The quantity required is always dependent on the type of fabric. For example, a cotton folding trailer tent will always require more shampoo than a boat cover, which is partly made of plastic.
Below is a rough guide.
1 litre = treats 6 to 14 m²
By cleaning the canvas with regular lukewarm water first, it is already saturated with water. Then spray the tent cloth with Sprayhood & Tent Shampoo. This way, it will be easier to use.
Click here for directions for use: Cleaning & impregnating your tent