Type this question into any forum and you'll get a different answer from every commenter, usually with a calculator attached. So let's do something unusual for the internet and give you the real numbers a surgical team actually works with.
Most patients here receive 3,500 to 4,000 grafts in a single procedure. What that means for your own head is the interesting part.
What a graft actually is
A graft is not a hair. Each graft is a tiny follicular unit holding one to four hairs, exactly as they grow naturally on your scalp, because hair doesn't grow in single strands so much as in little families.
Do the arithmetic on a full session and it comes to roughly 7,700 individual hairs, moved one by one in a single day. That's why a session of 3,500 to 4,000 grafts covers the majority of common hair loss patterns: it's enough to rebuild a hairline, fill a crown, and restore the density between them.
Why you can't just order more
Here's the constraint the forums skip past: the grafts come from you. FUE takes follicles from the back and sides of your head, where hair is genetically resistant to the hormone behind pattern baldness, and your donor area has to stay looking full after it has given what the front needs.
So the real question is never "how many grafts can I have?" but "what does my pattern need, and what can my donor hair comfortably give?" Those two numbers get balanced by the surgical team, and the balance is different on every head. That's also why the moved hair is permanent: the follicles carry their resistance with them wherever they're placed.
Getting your own number
Your number comes from two things a camera call can genuinely assess: your hair loss pattern, and your donor density. That's what the free video consultation is for, around thirty minutes, any evening from 6pm, with the team that would treat you.
You'll come away knowing your graft estimate, whether one day covers your pattern (for most people it does), and whether surgery is even the right tool, because for diffuse thinning the honest answer is often PRP instead. Real numbers, from the people who'd be doing the counting.