What Duolingo score do you need for Charles University?

Both pages say test results should not be older than two years and that comparable C1-level qualifications also meet the requirement. No Duolingo subscores are set.

Two years of previous education taught only in English in listed countries exempts you; the master's list adds India and Malta, and graduates of the faculty's English bachelor's are exempt too. The bachelor's page gives electronic codes for TOEFL, SAT, ACT and IB but no Duolingo sending instruction.

For comparison, the bachelor's page asks for IELTS 6.5 where it asks for Duolingo 110.

The pages list no conditional or pathway route. You would need another listed test, such as Cambridge C1 Advanced or TOEFL iBT 85, or a qualification showing C1 English.

Requirements vary by programme and change between admissions cycles. The score that binds you is the one on your Charles University programme page and in your offer letter, so check it there before you book a test.