Going from Persian (Farsi) to Korean (한국어) has a composite linguistic distance of 85% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Arabic → Hangul
Indo-European ↔ Koreanic
The 5 languages with the lowest linguistic distance from Persian (Farsi):
A quick 3-question check between Persian (Farsi) and Korean. No signup.