Going from Punjabi to Persian (Farsi) (فارسی) has a composite linguistic distance of 70% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Gurmukhi/Arabic → Arabic
Indo-European ↔ Indo-European
The 5 languages with the lowest linguistic distance from Punjabi:
A quick 3-question check between Punjabi and Persian (Farsi). No signup.