Start with length
Shorter lengths usually need less hair because each bundle carries more weft. Longer lengths often need more bundles for the same fullness.
Bundles guide
Bundle count depends on length, leave-out, closure or frontal use, and how full you want the finished style to look.
Shorter lengths usually need less hair because each bundle carries more weft. Longer lengths often need more bundles for the same fullness.
A closure or frontal can reduce the amount of leave-out needed, but many shoppers still choose three bundles for a full look.
If the install is planned weeks away, a monthly hair plan can help build toward a specific length set without changing the selection later.
Answers
Three bundles are common for many installs, but very long or very full styles may need more hair.
A closure can help complete the style with less leave-out and more protective coverage.