For a full sew-in:
8” – 12” we recommend 2 bundles;14” – 18” we recommend 3 bundles;20” – 26” we recommend 3-4 bundles;28” we recommend 4 bundles

For a closure or frontal install:
8” – 16” we recommend 2 bundles + closure or frontal;18” – 24” we recommend 3 bundles + closure or frontal;26” up we recommend 3-4 bundles + closure or frontal.

The hair you need is based on the size of your head and hair length also strongly depends on personal preference

See General Product Information for head measurements.