Consumption always depends on the type of cloth.
For example, the cotton canvas of a trailer tent will always absorb more shampoo than the canvas of a boat cover, which also contains a plastic component.
On average, you can use the following.
1 liter = 6 to 14 m²
By first cleaning the canvas with warm water, it is already saturated with water. Then spray the Sprayhood & Tent Shampoo on the canvas. It will then be easier to handle.