We cannot give you an exact answer as this will always depend on how long or thick your hair is.
If your hair is of average thickness and about shoulder length, you will usually need 1 vial of Water Colour. For longer or thicker hair you may need 2 or even 3 vials.
If you are applying to your roots only you may get 1 or 2 applications.
Tip: For the most efficient and economical way to apply - squeeze the required amount of Water Colour hair colour into a non-metallic bowl and apply with a hairdressers tint brush, this will help with application and make the colour go further.
You may be interested in our Hair Colouring Accessories.
Our friendly support team are here to help, so please do contact us.