What Duolingo score do you need for Prince Sultan University?

The undergraduate page says the tests are valid for two years from the test date. PSU accepts the Duolingo English Test, TOEFL iBT Home Edition and IELTS Online as online tests, subject to the provider's proctoring and compliance rules, and says a result may be cancelled if those rules are broken. PSU is not responsible for disputes over cancelled results; contact the test provider.

A high school diploma from an international school in Saudi Arabia, or from an English-medium school abroad that the Ministry of Education has equalised, also meets the undergraduate requirement.

For comparison, the same page sets IELTS Academic at an overall 4 for undergraduate entry.

Undergraduate applicants who meet none of the English criteria are admitted to the Intensive English Program (IEP), one semester before the Preparatory Year Program (PYP).

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