The amount of hair needed will depend on the length and thickness of your clients hair, and the type of extensions they are interested in. The average head of hair needs between 120-150 grams. Clients with thinner hair may only need 100-120 grams, whereas clients with thicker hair could use up to 180-200 grams. Please keep in mind, these are estimated amounts as the amount of hair needed will vary from client to client.